Implantable electroacupuncture device and method for treating dyslipidemia

ABSTRACT

An Implantable ElectroAcupuncture Device (IEAD) treats dyslipidemia conditions of a patient through application of stimulation pulses applied at acupoint ST40, or its underlying nerves saphenous and peroneal. The IEAD comprises an implantable, coin-sized, self-contained, leadless electroacupuncture device having at least two electrodes attached to an outside surface of its housing. The device generates stimulation pulses in accordance with a specified stimulation regimen. Power management circuitry within the device allows a primary battery, having a high internal impedance, to be used to power the device. The stimulation regimen generates stimulation pulses during a stimulation session of duration T3 minutes applied every T4 minutes. The duty cycle, or ratio T3/T4, is very low, no greater than 0.05. The low duty cycle and careful power management allow the IEAD to perform its intended function for several years.

RELATED APPLICATIONS

This application is a Continuation-In-Part (CIP) of U.S. patentapplication Ser. No. 13/622,497, filed Sep. 19, 2012, which applicationis incorporated herein by reference. This application also claims thebenefit of the following previously-filed provisional patentapplications, each of which is also incorporated herein by reference:

-   -   1. VT12-002-01, Electrode Configuration For Implantable        Electroacupuncture Device, filed Mar. 6, 2012, Appl. No.        61/606,995;    -   2 VT12-003-01. Boost Converter Output Control For Implantable        Electroacupuncture Device, filed Mar. 12, 2012, Appl. No.        61/609,875;    -   3 VT12-003-02, Boost Converter Circuit Surge Control For        Implantable Electroacupuncture Device Using Digital Pulsed        Shutdown, filed Jul. 16, 2012, Appl. No. 61/672,257;    -   4 VT12-004-01, Smooth Ramp-Up Stimulus Amplitude Control For        Implantable Electroacupuncture Device, filed Jul. 17, 2012,        Appl. No. 61/672,661;    -   5 VT12-005-01, Battery Transient Current Reduction In An        Implantable Electroacupuncture Device, filed Jul. 19, 2012,        Appl. No. 61/673,254;    -   6 VT12-006-01, Pulse Charge Delivery Control In An Implantable        Electroacupuncture Device, filed Jul. 23, 2012, Appl. No.        61/674,691;    -   7 VT12-008-01, Radial Feed-Through Packaging For An Implantable        Electroacupuncture Device, filed Jul. 26, 2012, Appl. No.        61/676,275.

BACKGROUND

Dyslipidemia is defined as an abnormal amount of lipids (e.g.,cholesterol and/or fat) in the blood. In developed countries, mostdyslipidemias are hyperlipidemias, i.e., an elevation of lipids (highcholesterol and/or fat) in the blood. Globally, about thirty ninepercent of adults have high cholesterol. A third of global ischemicheart disease is attributable to high cholesterol. And, raisedcholesterol is estimated to cause about 2.6 million deaths, which is4.5% of total deaths, and 29.7 million disability adjusted life years.It is a major cause of disease burden in both industrialized anddeveloping nations as a risk factor for ischemic heart disease andstroke. However, in high-income countries, the burden is even greaterwith about 50% of adults having raised cholesterol.

While high cholesterol is especially a problem in developed nations,other dyslipidemias or abnormalities of the lipids, may be problematic.In particular, triglycerides are an important measure of heart healthand increased triglycerides can increase one's risk of heart disease.Triglycerides are a type of fat in the blood. While triglycerides andcholesterol are both types of fats that circulate in the blood,triglycerides store unused calories and provide the body with energywhile cholesterol is used to build cells and some hormones.

Cholesterol is a waxy substance that is found in the fats (the lipids)in one's blood. While the body needs cholesterol to continue buildinghealthy cells, having high cholesterol can increase a patient's risk ofheart disease.

The existence of high cholesterol may lead to the development of fattydeposits in one's blood vessels that eventually make it difficult forenough blood to flow through the arteries. The heart may not get as muchoxygen rich blood as it needs, increasing the risk of a heart attack.Such decreased blood flow to the brain can cause a stroke.

High cholesterol, also called “hypercholesterolemia,” can be inherited,but it is often preventable and treatable. Lifestyle choices such as ahealthy diet and regular exercise are good modulators of cholesterol.Sometimes medication can be a good regulator of high cholesterol aswell. Genetic factors also play into high cholesterol.

There are three different types of cholesterol: low-density lipoproteinor “LDL,” very-low-density lipoprotein or “VLDL,” and high-densitylipoprotein or “HDL.”

LDL, or “bad” cholesterol, transports cholesterol particles throughoutthe body. It builds up in the walls of the arteries making them hard andnarrow.

VLDL contains the most triglycerides, a type of fat, attached to theproteins in one's blood. VLDL cholesterol makes LDL cholesterol largerin size, which may cause the blood vessels to narrow. If a patient istaking cholesterol-lowering medication but has a high VLDL level, theymay need additional medication to lower the triglycerides.

HDL, which is sometimes called “good” cholesterol,” picks up excesscholesterol and takes it back to the liver.

The most common risk factors for high cholesterol are: smoking, obesity,poor diet, lack of exercise, high blood pressure, diabetes, and a familyhistory of heart disease.

Similarly, many of the same healthy choices that are likely to improvehigh cholesterol are also helpful to lowering triglyceride levels.Losing weight, cutting calories, avoiding and excess of sugar andrefined foods, limiting cholesterol in the diet, eating healthier fatsand fewer trans fats, reducing alcohol intake, and regular exercise willall help improve triglyceride levels.

High triglycerides may contribute to the hardening of the arteries orthickening of the artery wall increasing the risk of stroke, heartattack, and heart disease. High triglycerides might also be a sign ofanother condition like obesity and metabolic syndrome, among otherconditions that generally include an excess of fat at the abdomen, highblood pressure, high triglycerides, high blood sugar and abnormalcholesterol levels. It might also be a sign of poorly controlleddiabetes or a side effect of some medication.

An alternative approach for treating obesity, diabetes, high cholesteroland a host of other physiological conditions, illnesses, deficienciesand disorders is acupuncture, which includes traditional acupuncture andacupressure. Acupuncture has been practiced in Eastern civilizations(principally in China, but also in other Asian countries) for at least2500 years. It is still practiced today throughout many parts of theworld, including the United States and Europe. A good summary of thehistory of acupuncture, and its potential applications may be found inCheung, et al., “The Mechanism of Acupuncture Therapy and Clinical CaseStudies”, (Taylor & Francis, publisher) (2001) ISBN 0-415-27254-8,hereafter referred to as “Cheung, Mechanism of Acupuncture, 2001.” TheForward, as well as Chapters 1-3, 5, 7, 8, 12 and 13 of Cheung,Mechanism of Acupuncture, 2001, are incorporated herein by reference.

Despite the practice in Eastern countries for over 2500 years, it wasnot until President Richard Nixon visited China (in 1972) thatacupuncture began to be accepted in the West, such as the United Statesand Europe. One of the reporters who accompanied Nixon during his visitto China, James Reston, from the New York Times, received acupuncture inChina for post-operative pain after undergoing an emergency appendectomyunder standard anesthesia. Reston experienced pain relief from theacupuncture and wrote about it in The New York Times. In 1973 theAmerican Internal Revenue Service allowed acupuncture to be deducted asa medical expense. Following Nixon's visit to China, and as immigrantsbegan flowing from China to Western countries, the demand foracupuncture increased steadily. Today, acupuncture therapy is viewed bymany as a viable alternative form of medical treatment, alongsideWestern therapies. Moreover, acupuncture treatment is now covered, atleast in part, by most insurance carriers. Further, payment foracupuncture services consumes a not insignificant portion of healthcareexpenditures in the U.S. and Europe. See, generally, Cheung, Mechanismof Acupuncture, 2001, vii.

Acupuncture is an alternative medicine that treats patients by insertionand manipulation of needles in the body at selected points. See, Novak,Patricia D. et al (1995). Dorland's Pocket Medical Dictionary (25thed.), Philadelphia: (W.B. Saunders Publisher), ISBN 0-7216-5738-9. Thelocations where the acupuncture needles are inserted are referred toherein as “acupuncture points” or simply just “acupoints”. The locationof acupoints in the human body has been developed over thousands ofyears of acupuncture practice, and maps showing the location ofacupoints in the human body are readily available in acupuncture booksor online. For example, see, “Acupuncture Points Map,” found online at:http://www.acupuncturehealing.org/acupuncture-points-map.html. Acupointsare typically identified by various letter/number combinations, e.g.,L6, S37. The maps that show the location of the acupoints may alsoidentify what condition, illness or deficiency the particular acupointaffects when manipulation of needles inserted at the acupoint isundertaken.

References to the acupoints in the literature are not always consistentwith respect to the format of the letter/number combination. Someacupoints are identified by a name only, e.g., Tongli. The same acupointmay be identified by others by the name followed with a letter/numbercombination placed in parenthesis, e.g., Tongli (HT5). Alternatively,the acupoint may be identified by its letter/number combination followedby its name, e.g., HT5 (Tongli). The first letter typically refers to abody organ, or other tissue location associated with, or affected by,that acupoint. However, usually only the letter is used in referring tothe acupoint, but not always. Thus, for example, the acupoint ST40 isthe same as acupoint Stomach 40 which is the same as ST-40 which is thesame as ST 40 which is the same as Fenglong. For purposes of this patentapplication, unless specifically stated otherwise, all references toacupoints that use the same name, or the same first letter and the samenumber, and regardless of slight differences in second letters andformatting, are intended to refer to the same acupoint.

An excellent reference book that identifies all of the traditionalacupoints within the human body is WHO STANDARD ACUPUNCTURE POINTLOCATIONS IN THE WESTERN PACIFIC REGION, published by the World HealthOrganization (WHO), Western Pacific Region, 2008 (updated and reprinted2009), ISBN 978 92 9061 248 7 (hereafter “WHO Standard Acupuncture PointLocations 2008”). The Table of Contents, Forward (page v-vi) and GeneralGuidelines for Acupuncture Point Locations (pages 1-21), as well as page66 (which illustrates with particularity the location of acupoint ST40)of the WHO Standard Acupuncture Point Locations 2008 are incorporatedherein by reference. Moreover, the above-cited portions of the WHOStandard Acupuncture Point Locations 2008 reference book, with theexception of page 66, may be found as Appendix D in Applicant'searlier-filed patent application, U.S. patent application Ser. No.13/622,497, filed Sep. 19, 2012, which application is also incorporatedherein by reference. The relevant information from page 66 of the WHOStandard Acupuncture Point Locations 2008 book is presented herein asFIG. 1A, and accompanying text.

While many in the scientific and medical community are highly criticalof the historical roots upon which acupuncture has developed, (e.g.,claiming that the existence of meridians, qi, yin and yang, and the likehave no scientific basis), see, e.g.,http://en.wikipedia.org/wiki/Acupuncture, few can refute the vast amountof successful clinical and other data, accumulated over centuries ofacupuncture practice, that shows needle manipulation applied at certainacupoints is quite effective.

The World Health Organization and the United States' National Institutesof Health (NIH) have stated that acupuncture can be effective in thetreatment of neurological conditions and pain. Reports from the USA'sNational Center for Complementary and Alternative Medicine (NCCAM), theAmerican Medical Association (AMA) and various USA government reportshave studied and commented on the efficacy of acupuncture. There isgeneral agreement that acupuncture is safe when administered bywell-trained practitioners using sterile needles, but not on itsefficacy as a medical procedure.

An early critic of acupuncture, Felix Mann, who was the author of thefirst comprehensive English language acupuncture textbook Acupuncture:The Ancient Chinese Art of Healing, stated that “The traditionalacupuncture points are no more real than the black spots a drunkard seesin front of his eyes.” Mann compared the meridians to the meridians oflongitude used in geography—an imaginary human construct. Mann, Felix(2000). Reinventing acupuncture: a new concept of ancient medicine.Oxford: Butterworth-Heinemann. pp. 14; 31. ISBN 0-7506-4857-0. Mannattempted to combine his medical knowledge with that of Chinese theory.In spite of his protestations about the theory, however, he apparentlybelieved there must be something to it, because he was fascinated by itand trained many people in the West with the parts of it he borrowed. Healso wrote many books on this subject. His legacy is that there is now acollege in London and a system of needling that is known as “MedicalAcupuncture”. Today this college trains doctors and Western medicalprofessionals only.

For purposes of this patent application, the arguments for and againstacupuncture are interesting, but not that relevant. What is important isthat a body of literature exists that identifies several acupointswithin the human body that, rightly or wrongly, have been identified ashaving an influence on, or are otherwise somehow related to, thetreatment of various physiological conditions, deficiencies orillnesses, including obesity or overweight conditions. With respect tothese acupoints, the facts speak for themselves. Either these points door do not affect the conditions, deficiencies or illnesses with whichthey have been linked. The problem lies in trying to ascertain what isfact from what is fiction. This problem is made more difficult whenconducting research on this topic because the insertion of needles, andthe manipulation of the needles once inserted, is more of an art than ascience, and results from such research become highly subjective. Whatis needed is a much more regimented approach for doing acupunctureresearch.

It should also be noted that other medical research, not associated withacupuncture research, has over the years identified nerves and otherlocations throughout a patient's body where the application ofelectrical stimulation produces a beneficial effect for the patient.Indeed, the entire field of neurostimulation deals with identifyinglocations in the body where electrical stimulation can be applied inorder to provide a therapeutic effect for a patient. For purposes ofthis patent application, such known locations within the body aretreated essentially the same as acupoints—they provide a “target”location where electrical stimulation may be applied to achieve abeneficial result, whether that beneficial result is to reducecholesterol or triglyceride levels, to treat cardiovascular disease, totreat mental illness, or to address some other issue associated with adisease or condition of the patient.

Returning to the discussion regarding acupuncture, some have proposedapplying moderate electrical stimulation at selected acupuncture pointsthrough needles that have been inserted at those points. See, e.g.,http://en.wikipedia.org/wiki/Electroacupuncture. Such electricalstimulation is known as electroacupuncture (EA). According toAcupuncture Today, a trade journal for acupuncturists:“Electroacupuncture is quite similar to traditional acupuncture in thatthe same points are stimulated during treatment. As with traditionalacupuncture, needles are inserted on specific points along the body. Theneedles are then attached to a device that generates continuous electricpulses using small clips. These devices are used to adjust the frequencyand intensity of the impulse being delivered, depending on the conditionbeing treated. Electroacupuncture uses two needles at a time so that theimpulses can pass from one needle to the other. Several pairs of needlescan be stimulated simultaneously, usually for no more than 30 minutes ata time.” “Acupuncture Today: Electroacupuncture”. 2004 Feb. 1 (retrievedon-line 2006 Oct. 9 athttp://www.acupuncturetoday.com/abc/electroacupuncture.php).

U.S. Pat. No. 6,735,475, issued to Whitehurst et al., discloses use ofan implantable miniature neurostimulator, referred to as a“microstimulator,” that can be implanted into a desired tissue locationand used as a therapy for headache and/or facial pain. Themicrostimulator has a tubular shape, with electrodes at each end.

Other patents of Whitehurst et al. teach the use of this small,microstimulator, placed in other body tissue locations, including withinan opening extending through the skull into the brain, for the treatmentof a wide variety of conditions, disorders and diseases. See, e.g., U.S.Pat. No. 6,950,707 (obesity and eating disorders); U.S. Pat. No.7,003,352 (epilepsy by brain stimulation); U.S. Pat. No. 7,013,177 (painby brain stimulation); U.S. Pat. No. 7,155,279 (movement disordersthrough stimulation of Vagus nerve with both electrical stimulation anddrugs); U.S. Pat. No. 7,292,890 (Vagus nerve stimulation); U.S. Pat. No.7,203,548 (cavernous nerve stimulation); U.S. Pat. No. 7,440,806(diabetes by brain stimulation); U.S. Pat. No. 7,610,100(osteoarthritis); and U.S. Pat. No. 7,657,316 (headache by stimulatingmotor cortex of brain).

Techniques for using electrical devices, including external EA devices,for stimulating peripheral nerves and other body locations for treatmentof various maladies are known in the art. See, e.g., U.S. Pat. Nos.4,535,784; 4,566,064; 5,195,517; 5,250,068; 5,251,637; 5,891,181;6,393,324; 6,006,134; 7,171,266; and 7,171,266. The methods and devicesdisclosed in these patents, however, typically utilize (i) largeimplantable stimulators having long leads that must be tunneled throughtissue over an extended distance to reach the desired stimulation site,(ii) external devices that must interface with implanted electrodes viapercutaneous leads or wires passing through the skin, or (iii)inefficient and power-consuming wireless transmission schemes. Suchdevices and methods are still far too invasive, or are ineffective, andthus are subject to the same limitations and concerns, as are thepreviously described electrical stimulation devices.

From the above, it is seen that there is a need in the art for a lessinvasive device and technique for electroacupuncture stimulation ofacupoints that does not require the continual use of needles insertedthrough the skin, or long insulated wires implanted or inserted intoblood vessels, for the purpose of treating dyslipidemia.

SUMMARY

One characterization of the invention described herein is an ImplantableElectroAcupuncture Device (IEAD) that treats dyslipidemia throughapplication of electroacupuncture (EA) stimulation pulses applied atacupoint ST40, or its underlying nerves, the peroneal and saphenousnerves. The IEAD includes: (1) a small IEAD housing having an electrodeconfiguration thereon that includes at least two electrodes, (2) pulsegeneration circuitry located within the IEAD housing that delivers EAstimulation pulses to the patient's body tissue at one of the specifiedlocations, (3) a primary battery also located within the IEAD housingthat provides the operating power for the IEAD to perform its intendedfunction, and (4) a sensor located within the IEAD housing that isresponsive to operating commands wirelessly communicated to the IEADfrom a non-implanted location. These operating commands allow limitedexternal control of the IEAD, such as ON/OFF and EA stimulation pulseamplitude adjustment.

In one preferred embodiment, the IEAD housing used as part of theinvention is coin-sized and -shaped, having a nominal diameter of 23 mm,and a thickness of only 2 to 3 mm.

One preferred embodiment provides a symmetrical electrode configurationon the housing of the IEAD. Such symmetrical electrode configurationincludes at least two electrodes, at least one of which is locatedsubstantially in the center of a first surface of the IEAD housing, andis referred to as a central electrode. The other electrode issymmetrically positioned around and at least 5 mm distant from thecenter of the central electrode, and is referred to as an annular orring electrode (or, in some instances, as a circumscribing electrode).This symmetry between the central electrode and the annular electrodeadvantageously focuses the electric field, and hence the EA stimulationcurrent created by application of an EA stimulation pulse to theelectrodes, deep into the tissue below the central electrode, where thedesired EA stimulation occurs. Hence, when implanted, the first surfaceof the IEAD housing is faced inwardly into the patient's tissue below aspecified location on the surface of the patient's skin, e.g., aspecified acupoint, and a second surface of the IEAD housing, on theopposite side of the housing from the first surface, is faced outwardlyto the patient's skin. One preferred embodiment of the IEAD housing usesone centrally located cathode electrode on the first surface of the IEADhousing, and one ring anode electrode located on a perimeter edge of acoin-sized and -shaped IEAD housing.

The pulse generation circuitry located within the IEAD housing iscoupled to the at least two electrodes. This pulse generation circuitryis configured to generate EA stimulation pulses in accordance with aspecified stimulation regimen. This stimulation regimen defines theduration and rate at which a stimulation session is applied to thepatient. The stimulation regimen requires that the stimulation sessionhave a duration of no more than T3 minutes and a rate of occurrence ofno more than once every T4 minutes. Advantageously, the duty cycle ofthe stimulation sessions, i.e., the ratio of T3/T4, is very low, nogreater than 0.05. A representative value for T3 is 30 minutes, and arepresentative value for T4 is 7 days. The individual EA stimulationpulses that occur within the stimulation session also have a duty cyclemeasured relative to the period (where the “period” is the time intervalequal to the inverse of the frequency or rate of the stimulation pulses)of no greater than 1%. A representative pulse width and frequency forthe EA stimulation pulses is 0.1 milliseconds, occurring at a pulse rateof 2 Hz.

The primary battery contained within the IEAD housing and electricallycoupled to the pulse generation circuitry has a nominal output voltageof 3 volts, and an internal battery impedance that is at least 5 ohms,and may be as high as 150 ohms or more. Advantageously, electroniccircuitry within the IEAD housing controls the value of theinstantaneous surge current that may be drawn from the battery in orderto prevent any large drops in the battery output voltage. Avoiding largedrops in the battery output voltage assures that the circuits within theIEAD will continue to operate as designed without failure. Being able touse a primary battery that has a relatively high internal impedanceallows the battery to be thinner, and thus allows the device to bethinner and more easily implanted. The higher internal impedance alsoopens the door to using relatively inexpensive commercially-availabledisc batteries as the primary battery within the IEAD, thereby greatlyenhancing the manufacturability of the IEAD and significantly loweringits cost.

Another characterization of the invention described herein may bedescribed as a first method for treating dyslipidemia in a patient usinga leadless, coin-sized implantable electroacupuncture device (IEAD).Such IEAD is powered by a small disc battery having a specified nominaloutput voltage of about 3.0 volts, and having an internal impedance ofat least 5 ohms.

The IEAD used to practice this first method is configured, usingelectronic circuitry within the IEAD, to generate EA stimulation pulsesin accordance with a specified stimulation regimen. The EA stimulationpulses generated in accordance with this stimulation regimen are appliedto the patient's tissue through at least two electrodes located on thehousing of the IEAD. These two electrodes include at least one centralelectrode, located in the center of a bottom surface of the IEADhousing, and at least one annular electrode that surrounds the centralelectrode. The edge of the annular electrode closest to the centralelectrode is separated from the center of the central electrode by atleast 5 mm.

Using such an IEAD, the cardiovascular disease treatment provided bythis first method includes the steps of: (a) implanting the IEAD belowthe skin surface of the patient at acupoint ST40, or at a location nearthe nerves underlying acupoint ST40, the peroneal or saphenous nerves,with a bottom surface of the IEAD (the “bottom” surface of the IEAD isthat surface on which the central electrode is placed) facing into thepatient's tissue below the patient's skin surface at the targetlocation; and (b) enabling the IEAD to provide stimulation pulses inaccordance with a specified stimulation regimen.

The specified stimulation regimen, when enabled, provides a stimulationsession at a rate of once every T4 minutes, with each stimulationsession having a duration of T3 minutes. The ratio of T3/T4 must be nogreater than 0.05. A preferred stimulation session time T3 is 30minutes, but T3 could be as short as 10 minutes or as long as 60minutes. A preferred time between stimulation sessions, T4, is 7 days,but it could be as short as 1 day or as long as 14 days, as needed, tosuit the needs of a particular patient. In some embodiments, the timeperiod between stimulation sessions, T4, may itself be a variable thatincreases from an initial value, T4(min), to a final value, T4(final),where T4(min) is a desired initial value, e.g., 1 day (1440 minutes),and T4(final) is a desired final value, e.g., 7 days (10,080 minutes).In such situation, i.e., where T4 initially varies, the change of T4between T4(min) to T4(final) follows a prescribed ramp-up sequence,e.g., starting at T4(min), T4 doubles after each stimulation sessionuntil the desired value of T4(final) is reached. Thus, for example, ifT4(min) is 1 day, and T4(final) is 7 days, the value of T4 may vary asfollows once the stimulation sessions begin: T4=1 day, 2 days, 4 daysand 7 days.

Yet another characterization of the invention described herein is asecond method for treating patients with dyslipidemia. This secondmethod includes: (a) implanting a coin-sized electroacupuncture (EA)device in the patient just below the patient's skin at a targetstimulation site that includes acupoints ST40, or its underlying nerves,the peroneal and saphenous nerves; (b) enabling the EA device togenerate EA stimulation sessions at a duty cycle that is less than 0.05,wherein each stimulation session comprises a series of EA stimulationpulses; and (c) delivering the EA stimulation pulses of each stimulationsession to the target stimulation site through at least two electrodesattached to an outside surface of the EA device. The duty cycle of thestimulation sessions is the ratio of T3/T4, where T3 is the duration inminutes (or some other time unit) of each stimulation session, and T4 isthe time in minutes (or some other time unit that corresponds to thesame time unit used to define T3) between stimulation sessions.

In a preferred application for this second method, the electrodesattached to the outside surface of the EA device are arranged in asymmetrical pattern. This symmetrical pattern of electrodesadvantageously concentrates, or focuses, the electric field emanatingfrom the electrode(s) downward into the tissue below the targetstimulation site to a location where the electroacupuncture stimulationis most effective.

Additionally, the invention described herein may be characterized as amethod of assembling an implantable electroacupuncture device (IEAD) foruse in treating dyslipidemia, or some other similar abnormality of apatient. The IEAD is assembled so as to reside in a round, thin,hermetically-sealed, coin-sized housing. An important feature of thecoin-size housing, and the method of assembly associated therewith, isthat it electrically and thermally isolates a feed-through pin assemblyradially passing through a wall of the coin-sized housing from the hightemperatures associated with welding the housing closed to hermeticallyseal its contents. Such method of assembling includes the steps of:

-   -   a. forming a coin-sized housing having a bottom case and a top        cover plate, the top cover plate being adapted to fit over the        bottom case, the bottom case being substantially round and        having a diameter D2 that is nominally 23 mm and a perimeter        side wall extending all the way around the perimeter of the        bottom case, the perimeter side wall having a height W2, wherein        the ratio of W2 to D2 is no greater than about 0.13;    -   b. forming a recess in one segment of the side wall, the recess        extending radially inwardly from the side wall to a depth D3,        and the recess having an opening in a bottom wall portion        thereof;    -   c. hermetically sealing a feed-through assembly in the opening        in the bottom of the recess, the feed-through assembly having a        feed-through pin that passes through the opening without        contacting the edges of the opening, a distal end of the pin        extending radially outward beyond the side wall of the bottom        case, and a proximal end of the feed-through pin extending        radially inward toward the center of the bottom case, whereby        the feed-through pin assembly is hermetically bonded to the        opening in the side wall at a location in the bottom of the        recess that is a distance D3 from the perimeter side wall,        thereby thermally isolating the feed-through assembly from the        high temperatures that occur at the perimeter side wall when the        cover plate is welded to the edge of the perimeter side wall;    -   d. attaching a central electrode to the thin, coin-sized housing        at a central location on the bottom outside surface of the        feed-through housing;    -   e. inserting an electronic circuit assembly, including a        battery, inside of the bottom case, and connecting the proximal        end of the feed-though pin to an output terminal of the        electronic circuit assembly, and electrically connecting the        bottom case to a reference terminal of the battery;    -   f. baking out the assembly to remove moisture, back filling with        a mixture of He/Ar inert gas, and then welding the top cover        plate to the edges of the side wall of the bottom case, thereby        hermetically sealing the electronic circuit assembly, including        the battery, inside of the thin, coin-sized IEAD housing;    -   g. leak testing the welded assembly to assure a desired level of        hermeticity has been achieved;    -   h. placing an insulating layer of non-conductive material around        the perimeter edge of the thin coin-sized housing, then placing        a circumscribing electrode over the insulating layer of        non-conductive material, and then electrically connecting the        distal end of the feed-through pin to the circumscribing        electrode; and    -   i. covering all external surface areas of the thin, coin-sized        housing with a layer of non-conductive material except for the        circumscribing electrode around the perimeter of the coin-sized        housing and the central electrode centrally located on the        bottom surface of the thin-coin-sized housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the inventionwill be more apparent from the following more particular descriptionthereof, presented in conjunction with the following drawings. Thesedrawings illustrate various embodiments of the principles describedherein and are part of the specification. The illustrated embodimentsare merely examples and do not limit the scope of the disclosure.

FIG. 1 is a perspective view of an Implantable Electroacupuncture Device(IEAD) made in accordance with the teachings presented herein.

FIG. 1A illustrates the location of acupoint ST40 (also referred to asacupoint Fenglong), the acupoint identified herein that may serve as atarget stimulation site at which an IEAD may be implanted for thetreatment of a dyslipidemia conditions. The nerves underlying ST40, thesaphenous and/or peroneal nerves, may also serve as a target stimulationsite for the purpose of treating dyslipidemia.

FIG. 1B shows a sectional view of an IEAD implanted at a selected targetstimulation site, and illustrates the electric field gradient linescreated when an electroacupuncture (EA) pulse is applied to the tissuethrough the central electrode and ring electrode attached to the bottomsurface and perimeter edge, respectively, of the IEAD housing.

FIG. 2 shows a plan view of one surface of the IEAD housing illustratedin FIG. 1.

FIG. 2A shows a side view of the IEAD housing illustrated in FIG. 1.

FIG. 3 shows a plan view of the other side, indicated as the “BackSide,” of the IEAD housing or case (also referred to as the “skin side”)illustrated in FIG. 1.

FIG. 3A is a sectional view of the IEAD of FIG. 3 taken along the lineA-A of FIG. 3.

FIG. 4 is a perspective view of the IEAD housing, including afeed-through pin, before the electronic components are placed therein,and before being sealed with a cover plate.

FIG. 4A is a side view of the IEAD housing of FIG. 4.

FIG. 5 is a plan view of the empty IEAD housing shown in FIG. 4.

FIG. 5A depicts a sectional view of the IEAD housing of FIG. 5 takenalong the section line A-A of FIG. 5.

FIG. 5B shows an enlarged view or detail of the portion of FIG. 5A thatis encircled with the line B.

FIG. 6 is a perspective view of an electronic assembly, including abattery, adapted to fit inside of the empty housing of FIG. 4 and FIG.5.

FIGS. 6A and 6B show a plan view and side view, respectively, of theelectronic assembly shown in FIG. 6.

FIG. 7 is an exploded view of the IEAD assembly, illustrating itsconstituent parts.

FIG. 7A schematically illustrates a few alternative electrodeconfigurations that may be used with the invention.

FIG. 8A illustrates a functional block diagram of the electroniccircuits used within an IEAD of the type described herein.

FIG. 8B shows a basic boost converter circuit configuration, and is usedto model how the impedance of the battery R_(BAT) can affect itsperformance.

FIG. 9A illustrates a typical voltage and current waveform for thecircuit of FIG. 8 when the battery impedance R_(BAT) is small.

FIG. 9B shows the voltage and current waveform for the circuit of FIG.8B when the battery impedance R_(BAT) is large.

FIG. 10 shows one preferred boost converter circuit and a functionalpulse generation circuit configuration for use within the IEAD.

FIG. 11 shows an alternate boost converter circuit configuration and afunctional pulse generation circuit for use within the IEAD.

FIG. 12 shows a refinement of the circuit configuration of FIG. 11.

FIG. 13A shows one preferred schematic configuration for an implantableelectroacupunture device (IEAD) that utilizes the boost converterconfiguration shown in FIG. 10.

FIG. 13B shows current and voltage waveforms associated with theoperation of the circuit shown in FIG. 13A.

FIG. 14 shows another preferred schematic configuration for an IEADsimilar to that shown in FIG. 13A, but which uses an alternate outputcircuitry configuration for generating the stimulus pulses.

FIG. 15A shows a timing waveform diagram of representative EAstimulation pulses generated by the IEAD device during a stimulationsession.

FIG. 15B shows a timing waveform diagram of multiple stimulationsessions, and illustrates the waveforms on a more condensed time scale.

FIG. 16 shows a state diagram that depicts the various states the IEADmay assume as controlled by an external magnet.

Appendix A illustrates some examples of alternate symmetrical electrodeconfigurations that may be used with an IEAD of the type describedherein. Appendix A is not submitted herewith, but is found as Appendix Asubmitted with Applicant's earlier patent application, U.S. patentapplication Ser. No. 13/622,497, filed Sep. 19, 2012, (the “Parent”application of this application), which Parent application isincorporated herein by reference.

Appendix B illustrates a few examples of non-symmetrical electrodeconfigurations that may be used with an IEAD made in accordance with theteachings herein. Appendix B is not submitted herewith, but isincorporated herein by reference, and may be found as Appendix Bsubmitted with Applicant's earlier-filed Parent application (Ser. No.13/622.497, filed Sep. 19, 2012).

Appendix C shows an example of the code used in the micro-controller IC(e.g., U2 in FIG. 14) to control the basic operation and programming ofthe IEAD, e.g., to turn the IEAD ON/OFF, adjust the amplitude of thestimulus pulse, and the like, using only an external magnet as anexternal communication element. Appendix C is not submitted herewith,but is incorporated herein by reference, and may be found as Appendix Csubmitted with Applicant's earlier-filed Parent application (Ser. No.13/622.497, filed Sep. 19, 2012).

Appendices A, B, and C of Applicant's earlier-filed Parent applicationare incorporated by reference herein.

Throughout the drawings and appendices, identical reference numbersdesignate similar, but not necessarily identical, elements.

DETAILED DESCRIPTION

Overview

Disclosed and claimed herein is an implantable, self-contained, leadlesselectroacupuncture (EA) device having at least two electrode contactsmounted on the surface of its housing. The EA device disclosed herein isadapted to treat dyslipidemia in a patient. In one preferred embodiment,the electrodes on the surface of the EA device include a central cathodeelectrode on a bottom side of the housing, and an annular anodeelectrode that surrounds the cathode. In another preferred embodiment,the anode annular electrode is a ring electrode placed around theperimeter edge of the coin-shaped housing.

The EA device is leadless. This means there are no leads or electrodesat the distal end of leads (common with most implantable electricalstimulators) that have to be positioned and anchored at a desiredstimulation site. Also, because there are no leads, no tunneling throughbody tissue or blood vessels is required in order to provide a path forthe leads to return and be connected to a tissue stimulator (also commonwith most electrical stimulators).

The EA device is adapted to be implanted through a very small incision,e.g., less than 2-3 cm in length, directly adjacent to a selected targetstimulation site, e.g., an acupuncture site (“acupoint”) known tomoderate or affect an overweight, obese or excess body fat condition ofa patient.

The EA device is easy to implant. Also, most embodiments aresymmetrical. This means that there is no way that it can be implantedincorrectly (unless the physician puts it in up-side-down, which wouldbe difficult to do given the markings on its case). All that need bedone is to cut the incision, and slide the device in place through theincision. Once the implant pocket has been prepared, it is as easy assliding a coin into a slot. Such implantation can usually be completedin less than 10 minutes in an outpatient setting, or in a doctor'soffice. Only minor, local anesthesia need be used. No major orsignificant complications are envisioned for the implant procedure. TheEA device can also be easily and quickly explanted, if needed.

The EA device is self-contained. It includes a primary battery toprovide its operating power. It includes all of the circuitry it needs,in addition to the battery, to allow it to perform its intended functionfor several years. Once implanted, the patient will not even know it isthere, except for a slight tingling that may be felt when the device isdelivering stimulus pulses during a stimulation session. Also, onceimplanted, the patient can just forget about it. There are nocomplicated user instructions that must be followed. Just turn it on. Nomaintenance is needed. Moreover, should the patient want to disable theEA device, i.e., turn it OFF, or change stimulus intensity, he or shecan do so using, e.g., an external magnet.

The EA device can operate for several years because it is designed to bevery efficient. Stimulation pulses applied by the EA device at aselected target stimulation site, e.g., a specified acupoint, throughits electrodes formed on its case are applied at a very low duty cyclein accordance with a specified stimulation regimen. The stimulationregimen applies EA stimulation during a stimulation session that lastsat least 10 minutes, typically 30 minutes, and rarely longer than 60minutes. These stimulation sessions, however, occur at a very low dutycycle. In one preferred treatment regimen, for example, a stimulationsession having a duration of 30 minutes is applied to the patient justonce a week. The stimulation regimen, and the selected acupoint at whichthe stimulation is applied, are designed and selected to provideefficient and effective EA stimulation for the treatment of thepatient's overweight or obese condition.

The EA device is, compared to most implantable medical devices,relatively easy to manufacture and uses few components. This not onlyenhances the reliability of the device, but keeps the manufacturingcosts low, which in turn allows the device to be more affordable to thepatient. One key feature included in the mechanical design of the EAdevice is the use of a radial feed-through assembly to connect theelectrical circuitry inside of its housing to one of the electrodes onthe outside of the housing. The design of this radial feed-through pinassembly greatly simplifies the manufacturing process. The processplaces the temperature sensitive hermetic bonds used in the assembly—thebond between a pin and an insulator and the bond between the insulatorand the case wall—away from the perimeter of the housing as the housingis hermetically sealed at the perimeter with a high temperature laserwelding process, thus preserving the integrity of the hermetic bondsthat are part of the feed-through assembly.

In operation, the EA device is safe to use. There are no horrificfailure modes that could occur. Because it operates at a very low dutycycle (i.e., it is OFF much, much more than it is ON), it generateslittle heat. Even when ON, the amount of heat it generates is not much,less than 1 mW, and is readily dissipated. Should a component or circuitinside of the EA device fail, the device will simply stop working. Ifneeded, the EA device can then be easily explanted.

Another key feature included in the design of the EA device is the useof a commercially-available battery as its primary power source. Small,thin, disc-shaped batteries, also known as “coin cells,” are quitecommon and readily available for use with most modern electronicdevices. Such batteries come in many sizes, and use variousconfigurations and materials. However, insofar as the inventors orApplicant are aware, such batteries have never been used in implantablemedical devices previously. This is because their internal impedance is,or has always thought to have been, much too high for such batteries tobe of practical use within an implantable medical device where powerconsumption must be carefully monitored and managed so that the device'sbattery will last as long as possible, and so that dips in the batteryoutput voltage (caused by any sudden surge in instantaneous batterycurrent) do not occur that could compromise the performance of thedevice. Furthermore, the energy requirements of other active implantabletherapies are far greater than can be provided by such coin cellswithout frequent replacement.

The EA device disclosed herein advantageously employs power-monitoringand power-managing circuits that prevent any sudden surges in batteryinstantaneous current, or the resulting drops in battery output voltage,from ever occurring, thereby allowing a whole family ofcommercially-available, very thin, high-output-impedance, relatively lowcapacity, small disc batteries (or “coin cells”) to be used as the EAdevice's primary battery without compromising the EA device'sperformance. As a result, instead of specifying that the EA device'sbattery must have a high capacity, e.g., greater than 200 mAh, with aninternal impedance of, e.g., less than 5 ohms, which would eitherrequire a thicker battery and/or preclude the use ofcommercially-available coin-cell batteries, the EA device of the presentinvention can readily employ a battery having a relatively low capacity,e.g., less than 60 mAh, and a high battery impedance, e.g., greater than5 ohms.

Moreover, the power-monitoring, power-managing, as well as the pulsegeneration, and control circuits used within the EA device arerelatively simple in design, and may be readily fashioned fromcommercially-available integrated circuits (IC's) orapplication-specific integrated circuits (ASIC's), supplemented withdiscrete components, as needed. In other words, the electronic circuitsemployed within the EA device need not be complex nor expensive, but aresimple and inexpensive, thereby making it easier to manufacture and toprovide it to patients at an affordable cost.

A preferred application for an EA device made in accordance with theteachings presented herein is to treat dyslipidemia, also often referredto as the condition of having high cholesterol. Thus, the descriptionthat follows describes in much more detail an EA device that isespecially suited to be used to treat dyslipidemia. However, it is to beunderstood that the invention is not limited to treating only highcholesterol.

Definitions

As used herein, “annular”, “circumferential”, “circumscribing”,“surrounding” or similar terms used to describe an electrode orelectrode array, or electrodes or electrode arrays, (where the phrase“electrode or electrode array,” or “electrodes or electrode arrays,” isalso referred to herein as “electrode/array,” or “electrodes/arrays,”respectively) refers to an electrode/array shape or configuration thatsurrounds or encompasses a point or object, such as another electrode,without limiting the shape of the electrode/array or electrodes/arraysto be circular or round. In other words, an “annular” electrode/array(or a “circumferential” electrode/array, or a “circumscribing”electrode/array, or a “surrounding” electrode/array), as used herein,may be many shapes, such as oval, polygonal, starry, wavy, and the like,including round or circular. “Nominal” or “about” when used with amechanical dimension, e.g., a nominal diameter of 23 mm, means thatthere is a tolerance associated with that dimension of no more than plusor minus (+/−) 5%. Thus, a dimension that is nominally 23 mm means adimension of 23 mm+/−1.15 mm (0.05×23 mm=1.15 mm). “Nominal” when usedto specify a battery voltage is the voltage by which the battery isspecified and sold. It is the voltage you expect to get from the batteryunder typical conditions, and it is based on the battery cell'schemistry. Most fresh batteries will produce a voltage slightly morethan their nominal voltage. For example, a new nominal 3 volt lithiumcoin-sized battery will measure more than 3.0 volts, e.g., up to 3.6volts under the right conditions. Since temperature affects chemicalreactions, a fresh warm battery will have a greater maximum voltage thana cold one. For example, as used herein, a “nominal 3 volt” batteryvoltage is a voltage that may be as high as 3.6 volts when the batteryis brand new, but is typically between 2.7 volts and 3.4 volts,depending upon the load applied to the battery (i.e., how much currentis being drawn from the battery) when the measurement is made and howlong the battery has been in use.

As explained in more detail below, the essence of the inventionrecognizes that an electroacupunture modulation scheme need not becontinuous, thereby allowing the implanted EA device to use a small,high density, power source to provide such non-continuous EA modulation.(Here, it should be noted that “EA modulation,” as that phrase is usedherein, is the application of electrical stimulation pulses, at lowintensities, low frequencies and low duty cycles, to at least one of thetarget stimulation sites, e.g., an acupuncture site that has beenidentified as affecting a particular condition, e.g., dyslipidemia, ofthe patient. As a result, the EA device can be very small. And, becausethe electrodes form an integral part of the housing of the EA device,the EA device may thus be implanted directly at (or very near to) thedesired target tissue location, e.g., the target stimulation site, suchas the target acupoint.

In summary, and as explained more fully below in conjunction with thedescription of the treatment method for treating dyslipidemia, the basicapproach of EA stimulation includes: (1) identify an acupoint(s) orother target stimulation site that may be used to treat or mediate theparticular illness, condition or deficiency that has manifest itself inthe patient, e.g., dyslipidemia; (2) implant an EA device, made asdescribed herein, so that its electrodes are located to be near or onthe identified acupoint(s) or other target stimulation site; (3) applyEA modulation, having a low intensity, low frequency, and low duty cyclethrough the electrode(s) of the EA device so that electrical stimulationpulses flow through the tissue at the target stimulation site followinga prescribed stimulation regimen over several weeks or months or years.At any time during this EA stimulation regimen, the patient's illness,condition or deficiency may be evaluated and, as necessary, theparameters of the EA modulation applied during the EA stimulationregimen may be adjusted or “tweaked” in order to improve the resultsobtained from the EA modulation.

Conditions Treated

Dyslipidemia is medically defined as an abnormal plasma lipid profile.The most common dyslipidemias are high total cholesterol, LDLcholesterol, Lp(a), and triglycerides; low levels of high-densitylipoprotein (HDL) cholesterol; and high levels of small dense LDLparticles. These abnormal lipid statuses can be found alone or incombination.

About 50% of U.S. adults have raised total cholesterol levels, and thevast majority of patients with atherosclerotic vascular disease havesome form of dyslipidemia.

Elevated levels of total cholesterol and LDL cholesterol, and low levelsof HDL are major yet modifiable risk factors for coronary heart diseaseand other forms of atherosclerotic vascular disease.

It is said that for each 1% decrease in LDL cholesterol, and each 1%increase in HDL cholesterol, the risk for cardiovascular events isreduced by 2-3% and 1-3% respectively.

In a study conducted by Xie et al., 102 patients were treated withelectroacupuncture at a single acupoint, ST40, while another 102patients were treated with a supplement called Xuezhikang. See, Xie, J.P., Liu, G. L., Qiao, J. L., Gu, Q., Gai, Y. N., Huang, S. F., . . . &Jia, J. J. (2009). Multi-central randomized controlled study onelectroacupuncture at Fenglong (ST 40) for regulating blood lipids. ChinAcupunc Moxibustion, 29, 345-348. Chinese with English Translation(hereafter, “Xie 2009”). Patients were given EA at different frequenciesof stimulation depending upon whether they had raised triglyceride orcholesterol levels.

In the EA group one month after the study, total cholesterol,triglycerides, and LDL decreased and HDL increased. Withelectroacupuncture at only one acupoint, the patients benefited as muchas is typically produced by statins, which are the most effective drugsfor lowering levels of total cholesterol and LDL. See also, Li, M., &Zhang, Y. (2007). Modulation of gene expression in cholesterol-loweringeffect of electroacupuncture at Fenglong acupoint (ST40): A cDNAmicroarray study. International journal of molecular medicine, 19(4),617-630 (hereafter, “Li 2007”).

In a study performing manual acupuncture on experimental obese rats withhigh cholesterol, total cholesterol decreased significantly whencompared to the control group over a period of two weeks. See, Xie, J.P., Nong, Y., Jia, J. J., Ll. W., ZHANG, L. F., OH EN, X., & GAO, Y.(2008). Efficacy comparison of needling Fenglong (ST40) and coordinatedacupoints for regulating blood lipid level in rats with hyperlipidemia.JOURNAL-BEIJING UNIVERSITY OF TRADITIONAL CHINESE MEDICINE, 31(2), 141.Chinese with English abstract (hereafter, “Xie 2008”).

Similarly, in a study utilizing electroacupuncture in experimental highcholesterol rats combined with cerebral ischemia, the group receiving EAat acupoints SP6 and ST40 had significant decreases in triglyceridelevels and LDL cholesterol after treatment. See, Ren, X. J., Si, Y. C.,& Ma, H. F. (2007). Influence of electroacupunture on NSE in rats withhyperlipidemia combined with cerebral ischemia JOURNAL-BEIJINGUNIVERSITY OF TRADITIONAL CHINESE MEDICINE, 30(2), 139 (hereafter, “Ren2007”). For another article showing the use of acupuncture at ST40 in ahigh cholesterol rat model to bring about reductions in triglyceridesand LDL levels, see also, Li, C. J., Cheng, X. S., Li, C. Y., Cui, M.Z., & Sun, Z. R. (2005). Regulative effects of acupuncture at Fenglongacupoints on the blood lipids of normal rats and those withhyperlipemia. English abstract. (hereafter, “Li 2005”).

In a study utilizing electroacupuncture at ST40 on 144 patients withhigh cholesterol, total cholesterol and triglycerides were reducedsimilar to the control group which took the drug provastatin. See,Zhang, T. F., Wan, W. J., Zhang, H. X., Li, J. W., Cai, G. W., & Zhou,L. (2006). Multi-center observation of electroacupuncture at Fenglongpoint in the treatment of hyperlipidemia. English abstract (hereafter,“Zhang 2006”). See also, ZHANG, H. X., HUANG, G. F., & ZHANG, T. F.(2006). Clinical effectiveness of electroacupuncture at Fenglong pointin the treatment of hyperlipidemia. Chinese Journal of Rehabilitation,6, 005. English abstract (hereafter, “Zhang 2006”).

Applicant believes neuromodulation of the deep peroneal nerve plays animportant role in the reduction of cholesterol from acupuncture. Inparticular, a study done by Wu and Hsu where the authors did fivedifferent kinds of experiments in experimental hypercholesterolemiarabbits, the results are highly suggestive of the involvement of thedeep peroneal nerve. See, Wu, C. C., & Hsu, C. J. (1979). Neurogenicregulation of lipid metabolism in the rabbit—A mechanism for thecholesterol-lowering effect of acupuncture. Atherosclerosis, 33(2),153-164 (hereafter, “Wu, Hsu 1979”). In those experiments, only oneacupoint called LR3 or “Taichong” was stimulated, sometimes unilaterallyand sometimes bilaterally. In two of the experiments, the deep peronealnerve was dissected and in both of those experiments the rabbits withdissection did poorer in modulation of cholesterol than those withintact deep peroneal nerves. In another experiment, “experiment three,”serum cholesterol levels were significantly lower 1-3 weeks afteracupuncture in the acupuncture group than in either the control group orthe blocked acupuncture group. “Blocked acupuncture” entailed theinjection of 1% novacain intramuscularly at one side of the acupointLR3, intended to block the sensory nerve receptors followed by needlingof that same point.

Given the success of acupuncture at ST40 and the location of thatacupoint in relationship to the deep peroneal nerve, the deep peronealnerve is likely implicated in consideration of the evidence above.

Locations Stimulated and Stimulation Paradigms/Regimens

Applicant has identified one acupoint most responsible and most idealfor application of its technological approach to treat dyslipidemia.That acupoint is ST40. The nerves underlying acupoint ST40—the saphenousand peroneal nerves—have also been identified by Applicant as targetstimulation points to treat dyslipidemia.

The acupoint ST40, also called “Fenglong,” is located on theanterolateral aspect of the leg, at the lateral border of the tibialisanterior muscle, about 8 B-cun superior to the prominence of the lateralmalleolus. See, WHO Standard Acupuncture Point Locations 2008, page 66.See also FIG. 1A. (Note: “8 B-cun” is a proportional bone (skeletal)measurement, and is explained in WHO Standard Acupuncture PointLocations 2008, pages 11-13, incorporated herein by reference.) Theacupoint ST40 is also identified as about one fingerbreadth (a middlefinger) lateral to its neighboring point, ST38. It is called ST40, ST40, Stomach 40, Fenglong, among other names; each name refers to thesame acupoint. Applicant identifies this acupoint as ST40 or Fenglong.Given the breadth of acupuncture practice across the world, there mayexist other names in acupuncture which refer to the same point.

Applicant has identified a frequency range as low as 2 Hz and as high as15 Hz for the ideal stimulation paradigm in this application. While mostof the studies utilizing only ST40 or ST40 in combination with only oneother point and achieving successful regulation of lipids use eitherhigh frequency or some variation of low and high-frequency, applicanthas selected a low-frequency paradigm based upon some work done inoverweight patients with a handful of acupoints and based upon thepracticality of low-frequency for the use of a small implantable device.

In one clinical study utilizing EA at ST40 alongside several otheracupoints and a frequency of 7 Hz, triglycerides, total cholesterol, andLDL cholesterol were greatly reduced while HDL cholesterol wasincreased. See, Li, L., & Wang, Z. Y. (2006). Clinical therapeuticeffects of body acupuncture and ear acupuncture on juvenile simpleobesity and effects on metabolism of blood lipids]. Zhongguo zhenjiu=Chinese acupuncture & moxibustion, 26(3), 173 (hereafter, “Li, Wang2006”).

In another study for which manual acupuncture and Tuina (which is a formof massage) was utilized at ST40 alongside several other acupoints,total cholesterol and triglycerides were successfully reduced. See,Li-qiu, L., Wei-zhi, G., & Xin, D. (2005). Treatment of simple obesityof stomach-intestine excessive heat type by acupuncture and Tuina.Journal of Acupuncture and Tuina Science, 3(2), 61-62 (hereafter,“Li-qiu 2005”). Because manual acupuncture is probably more similar tolow-frequency stimulation than high-frequency electrical stimulation,Applicant believes this is suggestive of efficacy with the use oflow-frequency. See also, Cheng, L., Chen, M. G., Yang, H., He, J. S.,Zhang, C. Y., & Xiao, C. Y. (2007). Influence of acupuncture on insulinresistance in simple obesity patients. Journal of Acupuncture and TuinaScience, 5(4), 245-249 (hereafter, “Cheng 2007”).

In a study conducted in Turkey by Cabioglu et al., 2 Hzelectroacupuncture at five acupoints achieved both weight loss andreductions in triglyceride and total cholesterol levels. See, Cabioglu,M. T., & Ergene, N. (2005). Electroacupuncture therapy for weight lossreduces serum total cholesterol, triglycerides, and LDL cholesterollevels in obese women. The American journal of Chinese medicine, 33(04),525-533 (hereafter, “Cabioglu 2005”). While the five acupoints did notinclude ST40, Applicant's preferred acupoint, it did include two pointsoverlying the saphenous and peroneal nerves thought by Applicant to beinvolved in success achieved through application of acupuncture atacupoint ST40.

In addition to constant wave low-frequency stimulation, Applicant hasidentified the use of Han's dilatation wave with a frequency of 2/100 Hzfor treatment of dyslipidemia. The application of Han's method generallyrefers to the use of a TENS (transcutaneous electrical nervestimulation) unit called a HANS unit or “Han's acupoint nervestimulation” unit. When referring to the use of HANS at 2/100 Hz, itmeans the unit was set at 2 Hz alternating with 100 Hz, each lasting forabout 3 seconds. Use of this type of frequency has proved successful inover one hundred patients in one study and about 50 in another. See,e.g., Zhang, T. F., Wan, W. J., Zhang, H. X., Li, J. W., Cai, G. W., &Zhou, L. (2006). Multi-center observation of electroacupuncture atFenglong point in the treatment of hyperlipidemia (hereafter, “Zhang2006”); ZHANG, H. X., HUANG, G. F., & ZHANG, T. F. (2006). Clinicaleffectiveness of electroacupuncture at Fenglong point in the treatmentof hyperlipidemia. Chinese Journal of Rehabilitation, 6, 005 (hereafter,“Zhang, Huang 2006”).

Applicant has identified a frequency range as low as about 1 Hz and ashigh as 15 Hz for the ideal stimulation paradigm in this application.This frequency selection is based upon the paradigm used by Cabioglu'sgroup in its six studies, by a transcutaneous electric nerve stimulationstudy previously mentioned, and by the successful use of manualacupuncture for bringing about weight loss. See e.g., Cabioglu 2008;Cabioglu 2006; Cabioglu, Ergene 2006; Cabioglu 2005; Cabioglu et al2007; Cabioglu 2007; Tian, D., Li, X., Shi, Y., Liu, Y., & Han, J.(2003). Study on the effect of transcutaneous electric nerve stimulationon obesity. Beijing da xue xue bao. Yi xue ban=Journal of PekingUniversity. Health sciences, 35(3), 277. Chinese with EnglishTranslation (hereafter, “Tian 2003”); Güçel, F., Bahar, B., Demirtas,C., Mit, S., &

evik, C. (2012). Influence of acupuncture on leptin, ghrelin, insulinand cholecystokinin in obese women: a randomised, sham-controlledpreliminary trial. Acupuncture in Medicine, 30(3), 203-207 (hereafter,“Gucel 2012”).

Advantageously, applicant has determined that low current or lowintensity stimulation is successful at bringing about improvement in anabnormal lipid profile at acupoint ST40, or the other target stimulationsites, previously identified. That this is so may be due, in part, tothe fact that there appears to be little electrical resistance at thesesites. Applicant has identified a suitable intensity between about oneand ten milliamps based upon its analysis of the current used insuccessful acupuncture studies. It does not appear high intensity isrequired except perhaps with the use of transcutaneous electric nervestimulation for which the skin must also be penetrated by electricalcurrent. In addition, manual acupuncture, which is thought to provide anintensity not as great as high current intensity delivered throughelectroacupuncture, has had a fair amount of success. See, e.g. Gucel2012, Cheng 2007, Zhi-Cheng, L., Feng-min, S., & Yi-zheng, W. (1995).Good Regulation of Acupuncture in Simple Obesity Patients withStomach-Intestine Excessive Heat Type [J]. CHINESE JOURNAL OF INTEGRATEDTRADITIONAL AND WESTERN MEDICINE, 3 (hereafter, “Zhi-cheng 1995”);Li-qiu, L Wei-zhi, G., & Xin, D. (2005), Treatment of simple obesity ofstomach-intestine excessive heat type by acupuncture and Tuina. Journalof Acupuncture and Tuina Science, 3(2), 61-62 (hereafter, Li-qiu 2005”);Qunli, W., & Zhicheng, L. (2005). Acupuncture treatment of simpleobesity. J Tradit Chin Med, 25(2), 90-4 (hereafter, “Qunli 2005”); Zhao,N. X., Guo, R. L., & Ren, Q. Y. (2004). Effect of Acupuncture Treatmenton Cellular Hemorheology, Cholesterol and Triglyceride of Simple ObesityPatients. WORLD JOURNAL OF ACUPUNCTURE MOXIBUSTION-BEIJING-, 14(3),24-27 (hereafter, “Zhao 2004”).

Because low current stimulation is more ideal for maintaining a smallbattery size, and further because the combination of manual acupunctureand EA stimulation using low current have proven successful, applicanthas chosen to limit its stimulation paradigm to the use of a lowstimulation current, e.g., 1 to 10 mA, in combination with a lowfrequency of stimulation, e.g., 1 to 15 Hz, unless Han's 2/100 Hzstimulation is employed.

Applicant has selected to use a pulse-width range of about 0.1 to 0.5milliseconds. While the Cabioglu studies utilized a narrower pulsewidth, Applicant is of the opinion that a narrow pulse width of, e.g.,0.05 milliseconds may prove more difficult in the recruitment of fibers.The chosen pulse width range is in line with one study done by Tian etal. See, Tian 2003.

The 2000 year history of acupuncture supports a fairly short stimulationduration and rate of occurrence. It supports a stimulation sessionduration as short as 20 minutes (though more ordinarily done in 30minute durations) and a rate of occurrence of stimulation sessions asshort as one occurrence each day and as long as once every other week(though more commonly once a week). Applicant has designed itsstimulation paradigm to include an ideal duration and rate of occurrencewith both the life of the EA device and a beneficial result for thepatient in mind. This stimulation paradigm includes: (1) a duration ofstimulation sessions between about 20 minutes and about 60 minutes, and(2) a rate of occurrence of the stimulation sessions of between aboutonce every other week to once daily.

Mechanical Design

Turning first to FIG. 1, there is shown a perspective view of onepreferred embodiment of an implantable electroacupuncture device (IEAD)100 that may be used to treat a dyslipidemia or similar condition inaccordance with the teachings disclosed herein. The IEAD 100 may alsosometimes be referred to as an implantable electroacupuncture stimulator(IEAS). As seen in FIG. 1, the IEAD 100 has the appearance of a disc orcoin, having a front side 106 (which is also labeled as the “CathodeSide”) 106, a back side (also referred to as the “Skin Side”) 102 (notvisible in FIG. 1) and an edge side 104.

As used herein, the “front” side of the IEAD 100 is the side that ispositioned so as to face the target stimulation point (e.g., the desiredacupoint) where EA stimulation is to be applied when the IEAD isimplanted. The “back” side is the side opposite the front side and isthe farthest away from the target stimulation point when the IEAD isimplanted. The “edge” of the IEAD is the side that connects or joins thefront side to the back side. In FIG. 1, the IEAD 100 is oriented to showthe front side 102 and a portion of the edge side 104.

Many of the features associated with the mechanical design of the IEAD100 shown in FIG. 1 are the subject of a prior U.S. Provisional patentapplication, entitled “Radial Feed-Through Packaging for An ImplantableElectroacupuncture Device”, Application No. 61/676,275, filed 26 Jul.2012, which application is incorporated here by reference.

It should be noted here that throughout this application, the terms IEAD100, IEAD housing 100, bottom case 124, can 124, or IEAD case 124, orsimilar terms, are used to describe the housing structure of the EAdevice. In some instances it may appear these terms are usedinterchangeably. However, the context should dictate what is meant bythese terms. As the drawings illustrate, particularly FIG. 7, there is abottom case 124 that comprises the “can” or “container” wherein thecomponents of the IEAD 100 are first placed and assembled duringmanufacture of the IEAD 100. When all of the components are assembledand placed within the bottom case 124, a cover plate 122 is welded tothe bottom case 124 to form the hermetically-sealed housing of the IEAD.The cathode electrode 110 is attached to the outside of the bottom case124 (which is the front side 102 of the device), and the ring anodeelectrode 120 is attached, along with its insulating layer 129, aroundthe perimeter edge 104 of the bottom case 124. Finally, a layer ofsilicone molding 125 covers the IEAD housing except for the outsidesurfaces of the anode ring electrode and the cathode electrode.

The embodiment of the IEAD 100 shown in FIG. 1 utilizes two electrodes,a cathode electrode 110 that is centrally positioned on the front side102 of the IEAD 100, and an anode electrode 120. The anode electrode 120is a ring electrode that fits around the perimeter edge 104 of the IEAD100. Not visible in FIG. 1, but which is described hereinafter inconnection with the description of FIG. 7, is a layer of insulatingmaterial 129 that electrically insulates the anode ring electrode 120from the perimeter edge 104 of the housing or case 124.

Not visible in FIG. 1, but a key feature of the mechanical design of theIEAD 100, is the manner in which an electrical connection is establishedbetween the ring electrode 120 and electronic circuitry carried insideof the IEAD 100. This electrical connection is established using aradial feed-through pin that fits within a recess formed in a segment ofthe edge of the case 124, as explained more fully below in connectionwith the description of FIGS. 5, 5A, 5B and 7.

In contrast to the feed-through pin that establishes electrical contactwith the anode electrode, electrical connection with the cathodeelectrode 110 is established simply by forming or attaching the cathodeelectrode 110 to the front surface 102 of the IEAD case 124. In order toprevent the entire case 124 from functioning as the cathode (which isdone to better control the electric fields established between the anodeand cathode electrodes), the entire IEAD housing is covered in a layerof silicone molding 125 (see FIG. 7), except for the outside surface ofthe anode ring electrode 120 and the cathode electrode 110.

The advantage of using a central cathode electrode and a ring anodeelectrode is described in U.S. Provisional Patent Application No.61/672,257, filed 6 Mar. 2012, entitled “Electrode Configuration forImplantable Electroacupuncture Device”, which application isincorporated herein by reference. One significant advantage of thiselectrode configuration is that it is symmetrical. That is, whenimplanted, the surgeon or other medical personnel performing the implantprocedure, need only assure that the cathode side of the IEAD 100, which(for the embodiment shown in FIGS. 1-7) is the front side of the device,faces the target tissue location that is to be stimulated. In addition,the IEAD must be implanted over the desired acupoint, or other tissuelocation, that is intended to receive the electroacupuncture (EA)stimulation. The orientation of the IEAD 100 is otherwise not important.

FIG. 1A illustrates the location of acupoint ST40 (also referred to asFenglong), the acupoint identified herein that serves as a targetstimulation site at which an IEAD may be implanted for the treatment ofa dyslipidemia condition. The nerves underlying acupoint ST40, thesaphenous and/or peroneal nerves, may also serve as a target stimulationsite for the purpose of treating dyslipidemia.

An implanted IEAD 100 is illustrated generally in FIG. 1B. Shown in FIG.1B is a sectional view of a limb 80 of the patient wherein an acupoint90 (e.g., acupoint ST40) has been identified that is to receiveacupuncture treatment (in this case electroacupuncture treatment). Anincision (not shown in FIG. 1B) is made into the limb 80 a shortdistance, e.g., 10-15 mm, away from the acupoint 90. A slot (parallel tothe limb) is formed at the incision by lifting the skin closest to theacupoint up at the incision. As necessary, the surgeon may form a pocketunder the skin at the acupoint location. The IEAD 100, with its top side102 being closest to the skin (and thus also referred to as the “SkinSide”), is then slid through the slot 84 into the pocket so that thecenter of the IEAD is located under the acupoint 90 on the skin surface.This implantation process is as easy as inserting a coin into a slot.With the IEAD 100 in place, the incision is sewn or otherwise closed,leaving the IEAD 100 under the skin 80 at the location of the acupoint90 where electroacupuncture (EA) stimulation is desired.

In this regard, it should be noted that while the target stimulationpoint is generally identified by an “acupoint,” which is typically shownin drawings and diagrams as residing on the surface of the skin, thesurface of the skin is not the actual target stimulation point. Rather,whether such stimulation comprises manual manipulation of a needleinserted through the skin at the location on the skin surface identifiedas an “acupoint”, or whether such stimulation comprises electricalstimulation applied through an electrical field oriented to causestimulation current to flow through the tissue at a prescribed depthbelow the acupoint location on the skin surface, the actual targettissue point to be stimulated is located beneath the skin at a depth d2that varies depending on the particular acupoint location. Whenstimulation is applied at the target tissue point, such stimulation iseffective at treating a selected condition of the patient, e.g., highcholesterol, because there is something in the tissue at that location,or near that location, such as a nerve, a tendon, a muscle, or othertype of tissue, that responds to the applied stimulation in a mannerthat contributes favorably to the treatment of the condition experiencedby the patient.

FIG. 1B illustrates a sectional view of the IEAD 100 implanted so as tobe centrally located under the skin at the selected acupoint 90, andover the acupoint axis line 92. Usually, for most patients, the IEAD 100is implanted at a depth d1 of approximately 2-4 mm under the skin. Thetop (skin) side 102 of the IEAD is nearest to the skin 80 of thepatient. The bottom (cathode) side 106 of the IEAD, which is the side onwhich the central cathode electrode 110 resides, is farthest from theskin. Because the cathode electrode 110 is centered on the bottom of theIEAD, and because the IEAD 100 is implanted so as to be centered underthe location on the skin where the acupoint 90 is located, the cathode110 is also centered over the acupoint axis line 92.

FIG. 1B further illustrates the electric field gradient lines 88 thatare created in the body tissue 86 surrounding the acupoint 90 and theacupoint axis line 92. (Note: for purposes herein, when reference ismade to providing EA stimulation at a specified acupoint, it isunderstood that the EA stimulation is provided at a depth ofapproximately d2 below the location on the skin surface where theacupoint is indicated as being located.) As seen in FIG. 1B, theelectric field gradient lines are strongest along a line that coincideswith, or is near to, the acupoint axis line 92. It is thus seen that oneof the main advantages of using a symmetrical electrode configurationthat includes a centrally located electrode surrounded by an annularelectrode is that the precise orientation of the IEAD within its implantlocation is not important. So long as one electrode is centered over thedesired target location, and the other electrode surrounds the firstelectrode (e.g., as an annular electrode), a strong electric fieldgradient is created that is aligned with the acupoint axis line. Thiscauses the EA stimulation current to flow along (or very near) theacupoint axis line 92, and will result in the desired EA stimulation inthe tissue at a depth d2 below the acupoint location indicated on theskin.

FIG. 2 shows a plan view of the “front” (or “cathode”) side 106 of theIEAD 100. As seen in FIG. 2, the cathode electrode 110 appears as acircular electrode, centered on the front side, having a diameter D1.The IEAD housing has a diameter D2 and an overall thickness or width W2.For the preferred embodiment shown in these figures, D1 is about 4 mm,D2 is about 23 mm and W2 is a little over 2 mm (2.2 mm).

FIG. 2A shows a side view of the IEAD 100. The ring anode electrode 120,best seen in FIG. 2A, has a width W1 of about 1.0 mm, or approximately ½of the width W2 of the IEAD.

FIG. 3 shows a plan view of the “back” (or “skin”) side of the IEAD 100.As will be evident from subsequent figure descriptions, e.g., FIGS. 5Aand 5B, the back side of the IEAD 100 comprises a cover plate 122 thatis welded in place once the bottom case 124 has all of the electroniccircuitry, and other components, placed inside of the housing.

FIG. 3A is a sectional view of the IEAD 100 of FIG. 1 taken along theline A-A of FIG. 3. Visible in this sectional view is the feed-throughpin 130, including the distal end of the feed-through pin 130 attachedto the ring anode electrode 120. Also visible in this section view is anelectronic assembly 133 on which various electronic components aremounted, including a disc-shaped battery 132. FIG. 3A furtherillustrates how the cover plate 122 is welded, or otherwise bonded, tothe bottom case 124 in order to form the hermetically-sealed IEADhousing 100.

FIG. 4 shows a perspective view of the IEAD case 124, including thefeed-through pin 130, before the electronic components are placedtherein, and before being sealed with the “skin side” cover plate 122.The case 124 is similar to a shallow “can” without a lid, having a shortside wall around its perimeter. Alternatively, the case 124 may beviewed as a short cylinder, closed at one end but open at the other.(Note, in the medical device industry the housing of an implanted deviceis often referred to as a “can”.) The feed-through pin 130 passesthrough a segment of the wall of the case 124 that is at the bottom of arecess 140 formed in the wall. The use of this recess 140 to hold thefeed-through pin 130 is a key feature of the invention because it keepsthe temperature-sensitive portions of the feed-through assembly (thoseportions that could be damaged by excessive heat) away from the thermalshock and residual weld stress inflicted upon the case 124 when thecover plate 122 is welded thereto.

FIG. 4A is a side view of the IEAD case 124, and shows an annular rim126 formed on both sides of the case 124. The ring anode electrode 120fits between these rims 126 once the ring electrode 120 is positionedaround the edge of the case 124. (This ring electrode 120 is, for mostconfigurations, used as an anode electrode. Hence, the ring electrode120 may sometimes be referred to herein as a ring anode electrode.However, it is noted that the ring electrode could also be employed as acathode electrode, if desired.) A silicone insulator layer 129 (see FIG.7) is placed between the backside of the ring anode electrode 120 andthe perimeter edge of the case 124 where the ring anode electrode 120 isplaced around the edge of the case 124.

FIG. 5 shows a plan view of the empty IEAD case 124 shown in theperspective view of FIG. 4. An outline of the recess cavity 140 is alsoseen in FIG. 5, as is the feed-through pin 130. A bottom edge of therecess cavity 140 is located a distance D5 radially inward from the edgeof the case 124. In one embodiment, the distance D5 is between about 2.0to 2.5 mm. The feed-through pin 130, which is just a piece of solidwire, is shown in FIG. 5 extending radially outward from the case 124above the recess cavity 140 and radially inward from the recess cavitytowards the center of the case 124. The length of this feed-through pin130 is trimmed, as needed, when a distal end (extending above therecess) is connected (welded) to the anode ring electrode 120 (passingthrough a hole in the ring electrode 120 prior to welding) and when aproximal end of the feed-through pin 130 is connected to an outputterminal of the electronic assembly 133.

FIG. 5A depicts a sectional view of the IEAD housing 124 of FIG. 5 takenalong the section line A-A of FIG. 5. FIG. 5B shows an enlarged view ordetail of the portion of FIG. 5A that is encircled with the line B.Referring to FIGS. 5A and 5B jointly, it is seen that the feed-throughpin 130 is embedded within an insulator material 136, which insulatingmaterial 136 has a diameter of D3. The feed-through pin assembly (whichpin assembly comprises the combination of the pin 130 embedded into theinsulator material 136) resides on a shoulder around an opening or holeformed in the bottom of the recess 140 having a diameter D4. For theembodiment shown in FIGS. 5A and 5B, the diameter D3 is 0.95-0.07 mm,where the −0.07 mm is a tolerance. (Thus, with the tolerance considered,the diameter D3 may range from 0.88 mm to 0.95 mm) The diameter D4 is0.80 mm with a tolerance of −0.06 mm. (Thus, with the toleranceconsidered, the diameter D4 could range from 0.74 mm to 0.80 mm).

The feed-through pin 130 is preferably made of pure platinum 99.95%. Apreferred material for the insulator material 136 is Ruby or alumina.The IEAD case 124, and the cover 122, are preferably made from titanium.The feed-through assembly, including the feed-through pin 130,ruby/alumina insulator 136 and the case 124 are hermetically sealed as aunit by gold brazing. Alternatively, active metal brazing can be used.(Active metal brazing is a form of brazing which allows metal to bejoined to ceramic without metallization.)

The hermeticity of the sealed IEAD housing is tested using a helium leaktest, as is common in the medical device industry. The helium leak rateshould not exceed 1×10⁻⁹ STD cc/sec at 1 atm pressure. Other tests areperformed to verify the case-to-pin resistance (which should be at least15×10⁶ Ohms at 100 volts DC), the avoidance of dielectric breakdown orflashover between the pin and the case 124 at 400 volts AC RMS at 60 Hzand thermal shock.

One important advantage provided by the feed-through assembly shown inFIGS. 4A, 5, 5A and 5B is that the feed-through assembly made from thefeed-through pin 130, the ruby insulator 136 and the recess cavity 140(formed in the case material 124) may be fabricated and assembled beforeany other components of the IEAD 100 are placed inside of the IEAD case124. This advantage greatly facilitates the manufacture of the IEADdevice.

Turning next to FIG. 6, there is shown a perspective view of anelectronic assembly 133. The electronic assembly 133 includes amulti-layer printed circuit (pc) board 138, or equivalent mountingstructure, on which a battery 132 and various electronic components 134are mounted. This assembly is adapted to fit inside of the empty bottomhousing 124 of FIG. 4 and FIG. 5.

FIGS. 6A and 6B show a plan view and side view, respectively, of theelectronic assembly 133 shown in FIG. 6. The electronic components areassembled and connected together so as to perform the circuit functionsneeded for the IEAD 100 to perform its intended functions. These circuitfunctions are explained in more detail below under the sub-heading“Electrical Design”. Additional details associated with these functionsmay also be found in many of the co-pending patent applicationsreferenced above in Paragraph [0001].

FIG. 7 shows an exploded view of the complete IEAD 100, illustrating itsmain constituent parts. As seen in FIG. 7, the IEAD 100 includes,starting on the right and going left, a cathode electrode 110, a ringanode electrode 120, an insulating layer 129, the bottom case 124 (the“can” portion of the IEAD housing, and which includes the feed-throughpin 130 which passes through an opening in the bottom of the recess 140formed as part of the case, but wherein the feed-through pin 130 isinsulated and does not make electrical contact with the metal case 124by the ruby insulator 136), the electronic assembly 133 (which includesthe battery 132 and various electronic components 134 mounted on a pcboard 138) and the cover plate 122. The cover plate 122 is welded to theedge of the bottom case 124 using laser beam welding, or some equivalentprocess, as one of the final steps in the assembly process.

Other components included in the IEAD assembly, but not necessarilyshown or identified in FIG. 7, include adhesive patches for bonding thebattery 132 to the pc board 138 of the electronic assembly 133, and forbonding the electronic assembly 133 to the inside of the bottom of thecase 124. To prevent high temperature exposure of the battery 132 duringthe assembly process, conductive epoxy is used to connect a batteryterminal to the pc board 138. Because the curing temperature ofconductive epoxy is 125° C., the following process is used: (a) firstcure the conductive epoxy of a battery terminal ribbon to the pc boardwithout the battery, (b) then glue the battery to the pc board usingroom temperature cure silicone, and (c) laser tack weld the connectingribbon to the battery.

Also not shown in FIG. 7 is the manner of connecting the proximal end ofthe feed-through pin 130 to the pc board 138, and connecting a pc boardground pad to the case 124. A preferred method of making theseconnections is to use conductive epoxy and conductive ribbons, althoughother connection methods known in the art may also be used.

Further shown in FIG. 7 is a layer of silicon molding 125 that is usedto cover all surfaces of the entire IEAD 100 except for the anode ringelectrode 120 and the circular cathode electrode 110. An overmodlingprocess is used to accomplish this, although overmolding using siliconeLSR 70 (curing temperature of 120° C.) with an injection molding processcannot be used. Overmolding processes that may be used include: (a)molding a silicone jacket and gluing the jacket onto the case using roomtemperature cure silicone (RTV) inside of a mold, and curing at roomtemperature; (b) injecting room temperature cure silicone in a PEEK orTeflon® mold (silicone will not stick to the Teflon® or PEEK material);or (c) dip coating the IEAD 100 in room temperature cure silicone whilemasking the electrode surfaces that are not to be coated. (Note: PEEK isa well known semicrystalline thermoplastic with excellent mechanical andchemical resistance properties that are retained at high temperatures.)

When assembled, the insulating layer 129 is positioned underneath thering anode electrode 120 so that the anode electrode does not short tothe case 124. The only electrical connection made to the anode electrode120 is through the distal tip of the feed-through pin 130. Theelectrical contact with the cathode electrode 110 is made through thecase 124. However, because the entire IEAD is coated with a layer ofsilicone molding 125, except for the anode ring electrode 120 and thecircular cathode electrode 110, all stimulation current generated by theIEAD 100 must flow between the exposed surfaces of the anode andcathode.

It is noted that while the preferred configuration described herein usesa ring anode electrode 120 placed around the edges of the IEAD housing,and a circular cathode electrode 110 placed in the center of the cathodeside of the IEAD case 124, such an arrangement could be reversed, i.e.,the ring electrode could be the cathode, and the circular electrodecould be the anode.

Moreover, the location and shape of the electrodes may be configureddifferently than is shown in the one preferred embodiment describedabove in connection with FIGS. 1, and 2-7. For example, the ring anodeelectrode 120 need not be placed around the perimeter of the device, butsuch electrode may be a flat circumferential electrode that assumesdifferent shapes (e.g., round or oval) that is placed on the front orback surface of the IEAD so as to surround the central electrode.Further, for some embodiments, the surfaces of the anode and cathodeelectrodes may have convex surfaces.

It is also noted that while one preferred embodiment has been disclosedherein that incorporates a round, or short cylindrical-shaped housing,also referred to as a coin-shaped housing, the invention does notrequire that the case 124 (which may also be referred to as a“container”), and its associated cover plate 122, be round. The casecould just as easily be an oval-shaped, rectangular-shaped (e.g., squarewith smooth corners), polygonal-shaped (e.g., hexagon-, octagon-,pentagon-shaped), button-shaped (with convex top or bottom for asmoother profile) device. Any of these alternate shapes, or others,would still permit the basic principles of the invention to be used toprovide a robust, compact, thin, case to house the electronic circuitryand power source used by the invention; as well as to help protect afeed-through assembly from being exposed to excessive heat duringassembly, and to allow the thin device to provide the benefits describedherein related to its manufacture, implantation and use. For example, aslong as the device remains relatively thin, e.g., no more than about 2-3mm, and does not have a maximum linear dimension greater than about 25mm, then the device can be readily implanted in a pocket over the tissuearea where the selected acupoint(s) is located. As long as there is arecess in the wall around the perimeter of the case wherein thefeed-through assembly may be mounted, which recess effectively moves thewall or edge of the case inwardly into the housing a safe thermaldistance, as well as a safe residual weld stress distance, from theperimeter wall where a hermetically-sealed weld occurs, the principlesof the invention apply.

Further, it should be noted that while the preferred configuration ofthe IEAD described herein utilizes a central electrode on one of itssurfaces that is round, having a diameter of nominally 4 mm, suchcentral electrode need not necessarily be round. It could be ovalshaped, polygonal-shaped, or shaped otherwise, in which case its size isbest defined by its maximum width, which will generally be no greaterthan about 7 mm.

Finally, it is noted that the electrode arrangement may be modifiedsomewhat, and the desired attributes of the invention may still beachieved. For example, as indicated previously, one preferred electrodeconfiguration for use with the invention utilizes a symmetricalelectrode configuration, e.g., an annular electrode of a first polaritythat surrounds a central electrode of a second polarity. Such asymmetrical electrode configuration makes the implantableelectroacupuncture device (IEAD) relatively immune to being implanted inan improper orientation relative to the body tissue at the selectedacupoint(s) that is being stimulated. However, an electrodeconfiguration that is not symmetrical may still be used and many of thetherapeutic effects of the invention may still be achieved. For example,two spaced-apart electrodes on a front surface of the housing, one of afirst polarity, and a second of a second polarity, could still, whenoriented properly with respect to a selected acupoint tissue location,provide some desired therapeutic results.

FIG. 7A schematically illustrates a few alternative electrodeconfigurations that may be used with the invention. The electrodeconfiguration schematically shown in the upper left corner of FIG. 7A,identified as “I”, schematically illustrates one central electrode 110surrounded by a single round ring electrode 120. This is one of thepreferred electrode configurations that has been described previously inconnection, e.g., with the description of FIGS. 1, 1A, 1B and 7, and ispresented in FIG. 7A for reference and comparative purposes.

In the lower left corner of FIG. 7A, identified as “II”, anelectrode/array configuration is schematically illustrated that has acentral electrode 310 of a first polarity surrounded by an oval-shapedelectrode array 320 a of two electrodes of a second polarity. (Thisoval-shaped array 320 a could also be round.) When the two electrodes(of the same polarity) in the electrode array 320 a are properly alignedwith the body tissue being stimulated, e.g., aligned with a nerveunderlying the desired acupoint, then such electrode configuration canstimulate the body tissue (e.g., the underlying nerve) at or near thedesired acupoint(s) with the same, or almost the same, efficacy as canthe electrode configuration I (upper right corner of FIG. 7A).

Note, as has already been described above, the phrase “electrode orelectrode array,” or “electrodes or electrode arrays,” may also bereferred to herein as “electrode/array” or “electrodes/arrays,”respectively. For the ease of explanation, when an electrode array isreferred to herein that comprises a plurality (two or more) ofindividual electrodes of the same polarity, the individual electrodes ofthe same polarity within the electrode array may also be referred to as“individual electrodes”, “segments” of the electrode array, “electrodesegments”, or just “segments”.

In the lower right corner of FIG. 7A, identified as “III”, en electrodeconfiguration is schematically illustrated that has a round centralelectrode/array 310 b of three electrode segments of a first polaritysurrounded by an electrode array 320 b of three electrode segments of asecond polarity. (These round or oval shapes could be altered, asdesired or needed. That is, the round central electrode/array 310 bcould be an oval-shaped electrode array, and the oval-shaped electrodearray 320 b could be a round electrode array.) As shown in configurationIII of FIG. 7A, the three electrode segments of the electrode array 320b are symmetrically positioned within the array 320 b, meaning that theyare positioned more or less equidistant from each other. However, asymmetrical positioning of the electrode segments within the array isnot necessary to stimulate the body tissue at the desired acupoint(s)with some efficacy.

In the upper right corner of FIG. 7A, identified as “IV”, anelectrode/array configuration is schematically illustrated that has acentral electrode array 310 c of a first polarity surrounded by anelectrode array 320 c of four electrode segments of a second polarity.The four electrode segments of the electrode array 320 c are arrangedsymmetrically in a round or oval-shaped array. The four electrodesegments of the electrode array 310 c are likewise arrangedsymmetrically in a round or oval-shaped array. While preferred for manyconfigurations, the use of a symmetrical electrode/array, whether as acentral electrode array 310 or as a surrounding electrode/array 320, isnot always required.

The electrode configurations I, II, III and IV shown schematically inFIG. 7A are only representative of a few electrode configurations thatmay be used with the present invention. Further, it is to be noted thatthe central electrode/array 310 need not have the same number ofelectrode segments as does the surrounding electrode/array 320.Typically, the central electrode/array 310 of a first polarity will be asingle electrode; whereas the surrounding electrode/array 320 of asecond polarity may have n individual electrode segments, where n is aninteger that can vary from 1, 2, 3, . . . n. Thus, for a circumferentialelectrode array where n=4, there are four electrode segments of the samepolarity arranged in circumferential pattern around a centralelectrode/array. If the circumferential electrode array with n=4 is asymmetrical electrode array, then the four electrode segments will bespaced apart equally in a circumferential pattern around a centralelectrode/array. When n=1, the circumferential electrode array reducesto a single circumferential segment or a single annular electrode thatsurrounds a central electrode/array.

Additionally, the polarities of the electrode/arrays may be selected asneeded. That is, while the central electrode/array 310 is typically acathode (−), and the surrounding electrode/array 320 is typically ananode (+), these polarities may be reversed.

As has already been mentioned, the shape of the circumferentialelectrode/array, whether circular, oval, or other shape, need notnecessarily be the same shape as the IEAD housing, unless thecircumferential electrode/array is attached to a perimeter edge of theIEAD housing. The IEAD housing may be round, or it may be oval, or itmay have a polygon shape, or other shape, as needed to suit the needs ofa particular manufacturer and/or patient.

Additional electrode configurations, both symmetrical electrodeconfigurations and non-symmetrical electrode configurations, that may beused with an EA stimulation device as described herein, are illustratedin Appendix A and Appendix B.

Electrical Design

Next, with reference to FIGS. 8A-14, the electrical design and operationof the circuits employed within the IEAD 100 will be described. Moredetails associated with the design of the electrical circuits describedherein may be found in the following previously-filed U.S. patentapplications, which applications are incorporated herein by reference:(1) application Ser. No. 13/622,497, filed Sep. 19, 2012, entitledImplantable Electroacupuncture Device and Method for TreatingCardiovascular Disease; (2) Appl. No. 61/609,875, filed Mar. 12, 2012,entitled Boost Converter Output Control For ImplantableElectroacupuncture Device; (3) Appl. No. 61/672,257, filed Jul. 16,2012, entitled Boost Converter Circuit Surge Control For ImplantableElectroacupuncture Device Using Digital Pulsed Shutdown; (4) Appl. No.61/672,661, filed Jul. 17, 2012, entitled Smooth Ramp-Up StimulusAmplitude Control For Implantable Electroacupuncture Device; and (5)Appl. No. 61/674,691, filed Jul. 23, 2012, entitled Pulse ChargeDelivery Control In An Implantable Electroacupuncture Device.

FIG. 8A shows a functional block diagram of an implantableelectroacupuncture device (IEAD) 100 made in accordance with theteachings disclosed herein. As seen in FIG. 8A, the IEAD 100 uses animplantable battery 215 having a battery voltage V_(BAT). Also includedwithin the IEAD 100 is a Boost Converter circuit 200, an Output Circuit202 and a Control Circuit 210. The battery 115, boost converter circuit200, output circuit 202 and control circuit 210 are all housed within anhermetically sealed housing 124.

As controlled by the control circuit 210, the output circuit 202 of theIEAD 100 generates a sequence of stimulation pulses that are deliveredto electrodes E1 and E2, through feed-through terminals 206 and 207,respectively, in accordance with a prescribed stimulation regimen. Acoupling capacitor C_(C) is also employed in series with at least one ofthe feed-through terminals 206 or 207 to prevent DC (direct current)current from flowing into the patient's body tissue.

As explained more fully below in connection with the description ofFIGS. 15A and 15B, the prescribed stimulation regimen typicallycomprises a continuous stream of stimulation pulses having a fixedamplitude, e.g., V_(A) volts, a fixed pulse width, e.g., 0.5millisecond, and at a fixed frequency, e.g., 2 Hz, during eachstimulation session. The stimulation session, also as part of thestimulation regimen, is generated at a very low duty cycle, e.g., for 30minutes once each week. Other stimulation regimens may also be used,e.g., using a variable frequency for the stimulus pulse during astimulation session rather than a fixed frequency. Also, the rate ofoccurrence of the stimulation session may be varied from as short as,e.g., 1 day, to as long as, e.g., 14 days.

In one preferred embodiment, the electrodes E1 and E2 form an integralpart of the housing 124. That is, electrode E2 may comprise acircumferential anode electrode that surrounds a cathode electrode E1.The cathode electrode E1, for the embodiment described here, iselectrically connected to the case 124 (thereby making the feed-throughterminal 206 unnecessary).

In a second preferred embodiment, particularly well-suited forimplantable electrical stimulation devices, the anode electrode E2 iselectrically connected to the case 124 (thereby making the feed-throughterminal 207 unnecessary). The cathode electrode E1 is electricallyconnected to the circumferential electrode that surrounds the anodeelectrode E2. That is, the stimulation pulses delivered to the targettissue location (i.e., to the selected acupoint) through the electrodesE1 and E2 are, relative to a zero volt ground (GND) reference, negativestimulation pulses, as shown in the waveform diagram near the lowerright hand corner of FIG. 8A.

Thus, in the embodiment described in FIG. 8A, it is seen that during astimulation pulse the electrode E2 functions as an anode, or positive(+) electrode, and the electrode E1 functions as a cathode, or negative(−) electrode.

The battery 115 provides all of the operating power needed by the EAdevice 100. The battery voltage V_(BAT) is not the optimum voltageneeded by the circuits of the EA device, including the output circuitry,in order to efficiently generate stimulation pulses of amplitude, e.g.,−V_(A) volts. The amplitude V_(A) of the stimulation pulses is typicallymany times greater than the battery voltage V_(BAT). This means that thebattery voltage must be “boosted”, or increased, in order forstimulation pulses of amplitude V_(A) to be generated. Such “boosting”is done using the boost converter circuit 200. That is, it is thefunction of the Boost Converter circuit 200 to take its input voltage,V_(BAT), and convert it to another voltage, e.g., V_(OUT), which voltageV_(OUT) is needed by the output circuit 202 in order for the IEAD 100 toperform its intended function.

The IEAD 100 shown in FIG. 8A, and packaged as described above inconnection with FIGS. 1-7, advantageously provides a tinyself-contained, coin-sized stimulator that may be implanted in a patientat or near a specified acupoint in order to favorably treat a conditionor disease of a patient. The coin-sized stimulator advantageouslyapplies electrical stimulation pulses at very low levels and low dutycycles in accordance with specified stimulation regimens throughelectrodes that form an integral part of the housing of the stimulator.A tiny battery inside of the coin-sized stimulator provides enoughenergy for the stimulator to carry out its specified stimulation regimenover a period of several years. Thus, the coin-sized stimulator, onceimplanted, provides an unobtrusive, needleless, long-lasting, safe,elegant and effective mechanism for treating certain conditions anddiseases that have long been treated by acupuncture orelectroacupuncture.

A boost converter integrated circuit (IC) typically draws current fromits power source in a manner that is proportional to the differencebetween the actual output voltage V_(OUT) and a set point outputvoltage, or feedback signal. A representative boost converter circuitthat operates in this manner is shown in FIG. 8B. At boost converterstart up, when the actual output voltage is low compared to the setpoint output voltage, the current drawn from the power source can bequite large. Unfortunately, when batteries are used as power sources,they have internal voltage losses (caused by the battery's internalimpedance) that are proportional to the current drawn from them. Thiscan result in under voltage conditions when there is a large currentdemand from the boost converter at start up or at high instantaneousoutput current. Current surges and the associated under voltageconditions can lead to undesired behavior and reduced operating life ofan implanted electro-acupuncture device.

In the boost converter circuit example shown in FIG. 8A, the battery ismodeled as a voltage source with a simple series resistance. Withreference to the circuit shown in FIG. 8A, when the series resistanceR_(BAT) is small (5 Ohms or less), the boost converter input voltageV_(IN), output voltage V_(OUT) and current drawn from the battery,I_(BAT), typically look like the waveform shown in FIG. 9A, where thehorizontal axis is time, and the vertical axis on the left is voltage,and the vertical axis of the right is current.

Referring to the waveform in FIG. 9A, at boost converter startup (10ms), there is 70 mA of current drawn from the battery with only ˜70 mVof drop in the input voltage V_(IN). Similarly, the instantaneous outputcurrent demand for electro-acupuncture pulses draws up to 40 mA from thebattery with an input voltage drop of ˜40 mV.

Disadvantageously, however, a battery with higher internal impedance(e.g., 160 Ohms), cannot source more than a milliampere or so of currentwithout a significant drop in output voltage. This problem is depictedin the timing waveform diagram shown in FIG. 9B. In FIG. 9B, as in FIG.9A, the horizontal axis is time, the left vertical axis is voltage, andthe right vertical axis is current.

As seen in FIG. 9B, as a result of the higher internal batteryimpedance, the voltage at the battery terminal (V_(IN)) is pulled downfrom 2.9 V to the minimum input voltage of the boost converter (˜1.5 V)during startup and during the instantaneous output current loadassociated with electro-acupuncture stimulus pulses. The resulting dropsin output voltage V_(OUT) are not acceptable in any type of circuitexcept an uncontrolled oscillator circuit.

Also, it should be noted that although the battery used in the boostconverter circuit is modeled in FIG. 8B as a simple series resistor,battery impedance can arise from the internal design, battery electrodesurface area and different types of electrochemical reactions. All ofthese contributors to battery impedance can cause the voltage of thebattery at the battery terminals to decrease as the current drawn fromthe battery increases.

In a suitably small and thin implantable electroacupuncture device(IEAD) of the type disclosed herein, it is desired to use a higherimpedance battery in order to assure a small and thin device, keep costslow, and/or to have low self-discharge rates. The battery internalimpedance also typically increases as the battery discharges. This canlimit the service life of the device even if a new battery hasacceptably low internal impedance. Thus, it is seen that for the IEAD100 disclosed herein to reliably perform its intended function over along period of time, a circuit design is needed for the boost convertercircuit that can manage the instantaneous current drawn from V_(IN) ofthe battery. Such current management is needed to prevent the battery'sinternal impedance from causing V_(IN) to drop to unacceptably lowlevels as the boost converter circuit pumps up the output voltageV_(OUT) and when there is high instantaneous output current demand, asoccurs when EA stimulation pulses are generated.

To provide this needed current management, the IEAD 100 disclosed hereinemploys electronic circuitry as shown in FIG. 10, or equivalentsthereof. Similar to what is shown in FIG. 8B, the circuitry of FIG. 10includes a battery, a boost converter circuit 200, an output circuit230, and a control circuit 220. The control circuit 220 generates adigital control signal that is used to duty cycle the boost convertercircuit 200 ON and OFF in order to limit the instantaneous current drawnfrom the battery. That is, the digital control signal pulses the boostconverter ON for a short time, but then shuts the boost converter downbefore a significant current can be drawn from the battery. Inconjunction with such pulsing, an input capacitance C_(F) is used toreduce the ripple in the input voltage V_(IN). The capacitor C_(F)supplies the high instantaneous current for the short time that theboost converter is ON and then recharges more slowly from the batteryduring the interval that the boost converter is OFF.

In the circuitry shown in FIG. 10, it is noted that the output voltageV_(OUT) generated by the boost converter circuit 200 is set by thereference voltage V_(REF) applied to the set point or feedback terminalof the boost converter circuit 200. For the configuration shown in FIG.10, V_(REF) is proportional to the output voltage V_(OUT), as determinedby the resistor dividing network of R1 and R2.

The switches S_(P) and S_(R), shown in FIG. 10 as part of the outputcircuit 230, are also controlled by the control circuit 220. Theseswitches are selectively closed and opened to form the EA stimulationpulses applied to the load, R_(LOAD). Before a stimulus pulse occurs,switch S_(R) is closed sufficiently long for the circuit side ofcoupling capacitor C_(C) to be charged to the output voltage, V_(OUT).The tissue side of C_(C) is maintained at 0 volts by the cathodeelectrode E2, which is maintained at ground reference. Then, for most ofthe time between stimulation pulses, both switches S_(R) and Sp are keptopen, with a voltage approximately equal to the output voltage V_(OUT)appearing across the coupling capacitor C_(C).

At the leading edge of a stimulus pulse, the switch Sp is closed, whichimmediately causes a negative voltage −V_(OUT) to appear across theload, R_(LOAD), causing the voltage at the anode E1 to also drop toapproximately −V_(OUT), thereby creating the leading edge of thestimulus pulse. This voltage starts to decay back to 0 volts ascontrolled by an RC (resistor-capacitance) time constant that is longcompared with the desired pulse width. At the trailing edge of thepulse, before the voltage at the anode E1 has decayed very much, theswitch S_(P) is open and the switch S_(R) is closed. This action causesthe voltage at the anode E1 to immediately (relatively speaking) returnto 0 volts, thereby defining the trailing edge of the pulse. With theswitch S_(R) closed, the charge on the circuit side of the couplingcapacitor C_(C) is allowed to charge back to V_(OUT) within a timeperiod controlled by a time constant set by the values of capacitorC_(C) and resistor R3. When the circuit side of the coupling capacitorC_(C) has been charged back to V_(OUT), then switch S_(R) is opened, andboth switches S_(R) and S_(P) remain open until the next stimulus pulseis to be generated. Then the process repeats each time a stimulus pulseis to be applied across the load.

Thus, it is seen that in one embodiment of the electronic circuitry usedwithin the IEAD 100, as shown in FIG. 10, a boost converter circuit 200is employed which can be shut down with a control signal. The controlsignal is ideally a digital control signal generated by a controlcircuit 220 (which may be realized using a microprocessor or equivalentcircuit). The control signal is applied to the low side (ground side) ofthe boost converter circuit 200 (identified as the “shutdown” terminalin FIG. 10). A capacitor C_(F) supplies instantaneous current for theshort ON time that the control signal enables the boost convertercircuit to operate. And, the capacitor CF is recharged from the batteryduring the relatively long OFF time when the control signal disables theboost converter circuit.

An alternate embodiment of the electronic circuitry that may be usedwithin the IEAD 100 is shown in FIG. 11. This circuit is in mostrespects the same as the circuitry shown in FIG. 10. However, in thisalternate embodiment shown in FIG. 11, the boost converter circuit 200does not have a specific shut down input control. Rather, as seen inFIG. 11, the boost converter circuit is shut down by applying a controlvoltage to the feedback input of the boost converter circuit 200 that ishigher than V_(REF). When this happens, i.e., when the control voltageapplied to the feedback input is greater than V_(REF), the boostconverter will stop switching and draws little or no current from thebattery. The value of V_(REF) is typically a low enough voltage, such asa 1.2 V band-gap voltage, that a low level digital control signal can beused to disable the boost converter circuit. To enable the boostconverter circuit, the control signal can be set to go to a highimpedance, which effectively returns the node at the V_(REF) terminal tothe voltage set by the resistor divider network formed from R1 and R2.Alternatively the control signal can be set to go to a voltage less thanV_(REF).

A low level digital control signal that performs this function ofenabling (turning ON) or disabling (turning OFF) the boost convertercircuit is depicted in FIG. 11 as being generated at the output of acontrol circuit 220. The signal line on which this control signal ispresent connects the output of the control circuit 220 with the V_(REF)node connected to the feedback input of the boost converter circuit.This control signal, as suggested by the waveform shown in FIG. 11,varies from a voltage greater than V_(REF), thereby disabling or turningOFF the boost converter circuit, to a voltage less than V_(REF), therebyenabling or turning the boost converter circuit ON.

A refinement to the alternate embodiment shown in FIG. 11 is to use thecontrol signal to drive the low side of R2 as shown in FIG. 12. That is,as shown in FIG. 12, the boost converter circuit 200 is shut down whenthe control signal is greater than V_(REF) and runs when the controlsignal is less than V_(REF). A digital control signal can be used toperform this function by switching between ground and a voltage greaterthan V_(REF). This has the additional possibility of delta-sigmamodulation control of V_(OUT) if a measurement of the actual V_(OUT) isavailable for feedback, e.g., using a signal line 222, to thecontroller.

One preferred embodiment of the circuitry used in an implantableelectroacupuncture device (IEAD) 100 that employs a digital controlsignal as taught herein is shown in the schematic diagram shown in FIG.13A. In FIG. 13A, there are basically four integrated circuits (ICs)used as the main components. The IC U1 is a boost converter circuit, andperforms the function of the boost converter circuit 200 describedpreviously in connection with FIGS. 8B, 10, 11 and 12.

The IC U2 is a micro-controller IC and is used to perform the functionof the control circuit 220 described previously in connection with FIGS.10, 11 and 12. A preferred IC for this purpose is a MSP430G2452Imicro-controller chip made by Texas Instruments. This chip includes 8 KBof Flash memory. Having some memory included with the micro-controlleris important because it allows the parameters associated with a selectedstimulation regimen to be defined and stored. One of the advantages ofthe IEAD described herein is that it provides a stimulation regimen thatcan be defined with just 5 parameters, as taught below in connectionwith FIGS. 15A and 15B. This allows the programming features of themicro-controller to be carried out in a simple and straightforwardmanner.

The micro-controller U2 primarily performs the function of generatingthe digital signal that shuts down the boost converter to prevent toomuch instantaneous current from being drawn from the battery V_(BAT).The micro-controller U2 also controls the generation of the stimuluspulses at the desired pulse width and frequency. It further keeps trackof the time periods associated with a stimulation session, i.e., when astimulation session begins and when it ends.

The micro-controller U2 also controls the amplitude of the stimuluspulse. This is done by adjusting the value of a current generated by aProgrammable Current Source U3. In one embodiment, U3 is realized with avoltage controlled current source IC. In such a voltage controlledcurrent source, the programmed current is set by a programmed voltageappearing across a fixed resistor R5, i.e., the voltage appearing at the“OUT” terminal of U3. This programmed voltage, in turn, is set by thevoltage applied to the “SET” terminal of U3. That is, the programmedcurrent source U3 sets the voltage at the “OUT” terminal to be equal tothe voltage applied to the “SET” terminal. The programmed current thatflows through the resistor R5 is then set by Ohms Law to be the voltageat the “set” terminal divided by R5. As the voltage at the “set”terminal changes, the current flowing through resistor R5 at the “OUT”terminal changes, and this current is essentially the same as thecurrent pulled through the closed switch M1, which is essentially thesame current flowing through the load R_(LOAD). Hence, whatever currentflows through resistor R5, as set by the voltage across resistor R5, isessentially the same current that flows through the load R_(LOAD). Thus,as the micro-controller U2 sets the voltage at the “set” terminal of U3,on the signal line labeled “AMPSET”, it controls what current flowsthrough the load R_(LOAD). In no event can the amplitude of the voltagepulse developed across the load R_(LOAD) exceed the voltage V_(OUT)developed by the boost converter less the voltage drops across theswitches and current source.

The switches S_(R) and S_(P) described previously in connection withFIGS. 10, 11 and 12 are realized with transistor switches M1, M2, M3,M4, M5 and M6, each of which is controlled directly or indirectly bycontrol signals generated by the micro-controller circuit U2. For theembodiment shown in FIG. 13A, these switches are controlled by twosignals, one appearing on signal line 234, labeled PULSE, and the otherappearing on signal line 236, labeled RCHG (which is an abbreviation for“recharge”). For the circuit configuration shown in FIG. 13A, the RCHGsignal on signal line 236 is always the inverse of the PULSE signalappearing on signal line 234. This type of control does not allow bothswitch M1 and switch M2 to be open or closed at the same time. Rather,switch M1 is closed when switch M2 is open, and switch M2 is closed,when switch M1 is open. When switch M1 is closed, and switch M2 is open,the stimulus pulse appears across the load, R_(LOAD), with the currentflowing through the load, R_(LOAD), being essentially equal to thecurrent flowing through resistor R5. When the switch M1 is open, andswitch M2 is closed, no stimulus pulse appears across the load, and thecoupling capacitors C5 and C6 are recharged through the closed switch M2and resistor R6 to the voltage V_(OUT) in anticipation of the nextstimulus pulse.

The circuitry shown in FIG. 13A is only exemplary of one type of circuitthat may be used to control the pulse width, amplitude, frequency, andduty cycle of stimulation pulses applied to the load, R_(LOAD). Any typeof circuit, or control, that allows stimulation pulses of a desiredmagnitude (measured in terms of pulse width, frequency and amplitude,where the amplitude may be measured in current or voltage) to be appliedthrough the electrodes to the patient at the specified acupoint at adesired duty cycle (stimulation session duration and frequency) may beused. However, for the circuitry to perform its intended function over along period of time, e.g., years, using only a small energy source,e.g., a small coin-sized battery having a high battery impedance and arelatively low capacity, the circuitry must be properly managed andcontrolled to prevent excessive current draw from the battery.

It is also important that the circuitry used in the IEAD 100, e.g., thecircuitry shown in FIGS. 10, 11, 12, 13A, or equivalents thereof, havesome means for controlling the stimulation current that flows throughthe load, R_(LOAD), which load may be characterized as the patient'stissue impedance at and around the acupoint being stimulated. Thistissue impedance, as shown in FIGS. 11 and 12, may typically vary frombetween about 300 ohms to 2000 ohms. Moreover, it not only varies fromone patient to another, but it varies over time. Hence, there is a needto control the current that flows through this variable load, R_(LOAD).One way of accomplishing this goal is to control the stimulationcurrent, as opposed to the stimulation voltage, so that the same currentwill flow through the tissue load regardless of changes that may occurin the tissue impedance over time. The use of a voltage controlledcurrent source U3, as shown in FIG. 13A, is one way to satisfy thisneed.

Still referring to FIG. 13A, a fourth IC U4 is connected to themicro-controller U2. For the embodiment shown in FIG. 13A, the IC U4 isan electromagnetic field sensor, and it allows the presence of anexternally-generated (non-implanted) electromagnetic field to be sensed.An “electromagnetic” field, for purposes of this application includesmagnetic fields, radio frequency (RF) fields, light fields, and thelike. The electromagnetic sensor may take many forms, such as anywireless sensing element, e.g., a pickup coil or RF detector, a photondetector, a magnetic field detector, and the like. When a magneticsensor is employed as the electromagnetic sensor U4, the magnetic fieldis generated using an External Control Device (ECD) 240 thatcommunicates wirelessly, e.g., through the presence or absence of amagnetic field, with the magnetic sensor U4. (A magnetic field, or othertype of field if a magnetic field is not used, is symbolicallyillustrated in FIG. 13A by the wavy line 242.) In its simplest form, theECD 240 may simply be a magnet, and modulation of the magnetic field isachieved simply by placing or removing the magnet next to or away fromthe IEAD. When other types of sensors (non-magnetic) are employed, theECD 240 generates the appropriate signal or field to be sensed by thesensor that is used.

Use of the ECD 240 provides a way for the patient, or medical personnel,to control the IEAD 100 after it has been implanted (or before it isimplanted) with some simple commands, e.g., turn the IEAD ON, turn theIEAD OFF, increase the amplitude of the stimulation pulses by oneincrement, decrease the amplitude of the stimulation pulses by oneincrement, and the like. A simple coding scheme may be used todifferentiate one command from another. For example, one coding schemeis time-based. That is, a first command is communicated by holding amagnet near the IEAD 100, and hence near the magnetic sensor U4contained within the IEAD 100, for differing lengths of time. If, forexample, a magnet is held over the IEAD for at least 2 seconds, but nomore than 7 seconds, a first command is communicated. If a magnet isheld over the IEAD for at least 11 seconds, but no more than 18 seconds,a second command is communicated, and so forth.

Another coding scheme that could be used is a sequence-based codingscheme. That is, application of 3 magnetic pulses may be used to signalone external command, if the sequence is repeated 3 times. A sequence of2 magnetic pulses, repeated twice, may be used to signal anotherexternal command. A sequence of one magnetic pulse, followed by asequence of two magnetic pulses, followed by a sequence of threemagnetic pulses, may be used to signal yet another external command.

Other simple coding schemes may also be used, such as the letters AA,RR, HO, BT, KS using international Morse code. That is, the Morse codesymbols for the letter “A” are dot dash, where a dot is a short magneticpulse, and a dash is a long magnetic pulse. Thus, to send the letter Ato the IEAD 100 using an external magnet, the user would hold the magnetover the area where the IEAD 100 is implanted for a short period oftime, e.g., one second or less, followed by holding the magnet over theIEAD for a long period of time, e.g., more than one second.

More sophisticated magnetic coding schemes may be used to communicate tothe micro-controller chip U2 the operating parameters of the IEAD 100.For example, using an electromagnet controlled by a computer, the pulsewidth, frequency, and amplitude of the EA stimulation pulses used duringeach stimulation session may be pre-set. Also, the frequency of thestimulation sessions can be pre-set. Additionally, a master reset signalcan be sent to the device in order to re-set these parameters to defaultvalues. These same operating parameters and commands may be re-sent atany time to the IEAD 100 during its useful lifetime should changes inthe parameters be desired or needed.

The current and voltage waveforms associated with the operation of theIEAD circuitry of FIG. 13A are shown in FIG. 13B. In FIG. 13B, thehorizontal axis is time, the left vertical axis is voltage, and theright vertical axis is current. The battery in this example has 160 Ohmsof internal impedance.

Referring to FIGS. 13A and 13B, during startup, the boost converter ONtime is approximately 30 microseconds applied every 7.8 milliseconds.This is sufficient to ramp the output voltage V_(OUT) up to over 10 Vwithin 2 seconds while drawing no more than about 1 mA from the batteryand inducing only 150 mV of input voltage ripple.

The electroacupuncture (EA) simulation pulses resulting from operationof the circuit of FIG. 13A have a width of 0.5 milliseconds and increasein amplitude from approximately 1 mA in the first pulse to approximately15 mA in the last pulse. The instantaneous current drawn from thebattery is less than 2 mA for the EA pulses and the drop in batteryvoltage is less than approximately 300 mV. The boost converter isenabled (turned ON) only during the instantaneous output current surgesassociated with the 0.5 milliseconds wide EA pulses.

Another preferred embodiment of the circuitry used in an implantableelectroacupuncture device (IEAD) 100 that employs a digital controlsignal as taught herein is shown in the schematic diagram of FIG. 14.The circuit shown in FIG. 14 is, in most respects, very similar to thecircuit described previously in connection with FIG. 13A. What is new inFIG. 14 is the inclusion of a Schottky diode D4 at the output terminalLX of the boost convertor U1 and the inclusion of a fifth integratedcircuit (IC) U5 that essentially performs the same function as theswitches M1-M6 shown in FIG. 13A.

The Schottky diode D4 helps isolate the output voltage V_(OUT) generatedby the boost converter circuit U1. This is important in applicationswhere the boost converter circuit U1 is selected and operated to providean output voltage V_(OUT) that is four or five times as great as thebattery voltage, V_(BAT). For example, in the embodiment for which thecircuit of FIG. 14 is designed, the output voltage V_(OUT) is designedto be nominally 15 volts using a battery that has a nominal batteryvoltage of only 3 volts. (In contrast, the embodiment shown in FIG. 13Ais designed to provide an output voltage that is nominally 10-12 volts,using a battery having a nominal output voltage of 3 volts.)

The inclusion of the fifth IC U5 in the circuit shown in FIG. 14 is, asindicated, used to perform the function of a switch. The other ICs shownin FIG. 14, U1 (boost converter), U2 (micro-controller), U3 (voltagecontrolled programmable current source) and U4 (electromagnetic sensor)are basically the same as the IC's U1, U2, U3 and U4 describedpreviously in connection with FIG. 13A.

The IC U5 shown in FIG. 14 functions as a single pole/double throw(SPDT) switch. Numerous commercially-available ICs may be used for thisfunction. For example, an ADG1419 IC, available from Analog DevicesIncorporated (ADI) may be used. In such IC U5, the terminal “D”functions as the common terminal of the switch, and the terminals “SA”and “SB” function as the selected output terminal of the switch. Theterminals “IN” and “EN” are control terminals to control the position ofthe switch. Thus, when there is a signal present on the PULSE line,which is connected to the “IN” terminal of U5, the SPDT switch U5connects the “D” terminal to the “SB” terminal, and the SPDT switch U5effectively connects the cathode electrode E1 to the programmablecurrent source U3. This connection thus causes the programmed current,set by the control voltage AMPSET applied to the SET terminal of theprogrammable current source U3, to flow through resistor R5, which inturn causes essentially the same current to flow through the load,R_(LOAD), present between the electrodes E1 and E2. When a signal is notpresent on the PULSE line, the SPDT switch U5 effectively connects thecathode electrode E1 to the resistor R6, which allows the by the boostconverter circuit U2.

From the above description, it is seen that an implantable IEAD 100 isprovided that uses a digital control signal to duty-cycle limit theinstantaneous current drawn from the battery by a boost converter. Threedifferent exemplary configurations (FIGS. 10, 11 and 12) are taught forachieving this desired result, and two exemplary circuit designs thatmay be used to realize this result have been disclosed (FIGS. 13A and14). One configuration (FIG. 12) teaches the additional capability todelta-sigma modulate the boost converter output voltage.

Delta-sigma modulation is well described in the art. Basically, it is amethod for encoding analog signals into digital signals orhigher-resolution digital signals into lower-resolution digital signals.The conversion is done using error feedback, where the differencebetween the two signals is measured and used to improve the conversion.The low-resolution signal typically changes more quickly than thehigh-resolution signal and it can be filtered to recover the highresolution signal with little or no loss of fidelity. Delta-sigmamodulation has found increasing use in modern electronic components suchas converters, frequency synthesizers, switched-mode power supplies andmotor controllers. See, e.g., Wikipedia, Delta-sigma modulation.

II. F. Use and Operation

With the implantable electroacupuncture device (IEAD) 100 in hand, theIEAD 100 may be used most effectively to treat dyslipidemia by firstpre-setting stimulation parameters that the device will use during astimulation session. FIG. 15A shows a timing waveform diagramillustrating the EA stimulation parameters used by the IEAD to generateEA stimulation pulses. As seen in FIG. 15A, there are basically fourparameters associated with a stimulation session. The time T1 definesthe duration (or pulse width) of a stimulus pulse. The time T2 definesthe time between the start of one stimulus pulse and the start of thenext stimulus pulse. The time T2 thus defines the period associated withthe frequency of the stimulus pulses. The frequency of the stimulationpulses is equal to 1/T2. The ratio of T1/T2 is typically quite low,e.g., less than 0.01. The duration of a stimulation session is definedby the time period T3. The amplitude of the stimulus pulses is definedby the amplitude A1. This amplitude may be expressed in either voltageor current.

Turning next to FIG. 15B, a timing waveform diagram is shown thatillustrates the manner in which the stimulation sessions areadministered in accordance with a preferred stimulation regimen. FIG.15B shows several stimulation sessions of duration T3, and how often thestimulation sessions occur. The stimulation regimen thus includes a timeperiod T4 which sets the time period from the start of one stimulationsession to the start of the next stimulation session. T4 thus is theperiod of the stimulation session frequency, and the stimulation sessionfrequency is equal to 1/T4.

In order to allow the applied stimulation to achieve its desired effecton the body tissue at the selected target stimulation site, the periodof the stimulation session T4 may be varied when the stimulationsessions are first applied. This can be achieved by employing a simplealgorithm within the circuitry of the EA device that changes the valueof T4 in an appropriate manner. For example, at start up, the period T4may be set to a minimum value, T4(min). Then, as time goes on, the valueof T4 is gradually increased until a desired value of T4, T4(final) isreached.

By way of example, if T4(min) is 1 day, and T4(final) is 7 days, thevalue of T4 may vary as follows once the stimulation sessions begin:T4=1 day for the duration between the first and second stimulationsessions, then 2 days for the duration between the second and thirdstimulation sessions, then 4 days for the duration between the third andfourth stimulation sessions, and then finally 7 days for the durationbetween all subsequent stimulation sessions after the fourth stimulationsession.

Rather than increasing the value of T4 from a minimum value to a maximumvalue using a simple doubling algorithm, as described in the previousparagraph, an enhancement is to use a table of session durations andintervals whereby the automatic session interval can be shorter for thefirst week or so. For example the 1^(st) 30 minute session could bedelivered after 1 day. The 2^(nd) 30 minute session could be deliveredafter 2 days. The 3^(rd) 30 minute session could be delivered after 4days. Finally, the 4^(th) 30 minute session could be delivered for allsubsequent sessions after 7 days.

If a triggered session is delivered completely, it advances the therapyschedule to the next table entry.

Another enhancement is that the initial set amplitude only takes effectif the subsequent triggered session is completely delivered. If thefirst session is aborted by a magnet application, the device reverts toa Shelf Mode. In this way, the first session is always a triggeredsession that occurs in the clinician setting.

Finally, the amplitude and place in the session table are saved innon-volatile memory when they change. This avoids a resetting of thetherapy schedule and need to reprogram the amplitude in the event of adevice reset.

One preferred set of parameters to use to define a stimulation regimenare

-   -   T1=0.5 milliseconds    -   T2=500 milliseconds    -   T3=30 minutes    -   T4=7 days (10,080 minutes)    -   A1=6 volts (across 1 kOhm), or 6 milliamperes (mA)

It is to be emphasized that the values shown above for the stimulationregimen are representative of only one preferred stimulation regimenthat could be used. Other stimulation regimens that could be used, andthe ranges of values that could be used for each of these parameters,are as defined in the claims.

It is also emphasized that the ranges of values presented in the claimsfor the parameters used with the invention have been selected after manymonths of careful research and study, and are not arbitrary. Forexample, the ratio of T3/T4, which sets the duty cycle, has beencarefully selected to be very low, e.g., no more than 0.05. Maintaininga low duty cycle of this magnitude represents a significant change overwhat others have attempted in the implantable stimulator art. Not onlydoes a very low duty cycle allow the battery itself to be small (coincell size), which in turn allows the IEAD housing to be very small,which makes the IEAD ideally suited for being used without leads,thereby making it relatively easy to implant the device at the desiredstimulation site (e.g., acupoint), but it also limits the frequency andduration of stimulation sessions.

Limiting the frequency and duration of the stimulation sessions is a keyaspect of Applicant's invention because it recognizes that sometreatments, such as treating overweight conditions, are best done slowlyand methodically, over time, rather than quickly and harshly using largedoses of stimulation (or other treatments) aimed at forcing a rapidchange in the patient's condition. Moreover, applying treatments slowlyand methodically is more in keeping with traditional acupuncture methods(which, as indicated previously, are based on over 2500 years ofexperience). In addition, this slow and methodical conditioning isconsistent with the time scale for remodeling of the central nervoussystem needed to produce the sustained therapeutic effect. Thus,applicants have based their treatment regimens on theslow-and-methodical approach, as opposed to the immediate-and-forcedapproach adopted by many, if not most, prior art implantable electricalstimulators.

Once the stimulation regimen has been defined and the parametersassociated with it have been pre-set into the memory of themicro-controller circuit 220, the IEAD 100 needs to be implanted.Implantation is usually a simple procedure, and is described above inconnection, e.g., with the description of FIGS. 1A and 1B.

For treating the dyslipidemia conditions targeted by the inventiondescribed herein, e.g., high cholesterol, the specified acupoint(s) (ortarget tissue locations) at which the EA stimulation pulses should beapplied in accordance with a selected stimulation regimen are theacupoint ST40, or its underlying nerves, the saphenous and/or peronealnerves. As indicated previously, acupoint ST40 is located on theanterolateral aspect of the leg at the lateral border of the tibialisanterior muscle, about 8 B-cun (which is approximately 8 inches for apatient having an averaged-sized skeletal structure) superior to theprominence of the lateral malleolus. See FIG. 1A and WHO StandardAcupuncture Point Locations 2008, pages 11-13, 66.

After implantation, the IEAD must be turned ON, and otherwisecontrolled, so that the desired stimulation regimen or stimulationparadigm may be carried out. In one preferred embodiment, control of theIEAD after implantation, as well as anytime after the housing of theIEAD has been hermetically sealed, is performed as shown in the statediagram of FIG. 16. Each circle shown in FIG. 16 represents an operating“state” of the micro-controller U2 (FIG. 13A or 14). As seen in FIG. 16,the controller U2 only operates in one of six states: (1) a “SetAmplitude” state, (2) a “Shelf Mode” state, (3) a “Triggered Session”state, (4) a “Sleep” state, (5) an “OFF” state, and an (6) “AutomaticSession” state. The “Automatic Session” state is the state thatautomatically carries out the stimulation regimen using thepre-programmed parameters that define the stimulation regimen.

Shelf Mode is a low power state in which the IEAD is placed prior toshipment. After implant, commands are made through magnet application.Magnet application means an external magnet, typically a small hand-heldcylindrical magnet, is placed over the location where the IEAD has beenimplanted. With a magnet in that location, the magnetic sensor U4 sensesthe presence of the magnet and notifies the controller U2 of themagnet's presence.

From the “Shelf Mode” state, a magnet application for 10 seconds (M.10s) puts the IEAD in the “Set Amplitude” state. While in the “SetAmplitude” state, the stimulation starts running by generating pulses atzero amplitude, incrementing every five seconds until the patientindicates that a comfortable level has been reached. At that time, themagnet is removed to set the amplitude.

If the magnet is removed and the amplitude is non-zero ( M^A), thedevice continues into the “Triggered Session” so the patient receivesthe initial therapy. If the magnet is removed during “Set Amplitude”while the amplitude is zero ( M^Ā), the device returns to the ShelfMode.

The Triggered Session ends and stimulation stops after the session time(T_(S)) has elapsed and the device enters the “Sleep” state. If a magnetis applied during a Triggered Session (M), the session aborts to the“OFF” state. If the magnet remains held on for 10 seconds (M.10 s) whilein the “OFF” state, the “Set Amplitude” state is entered with thestimulation level starting from zero amplitude as described.

If the magnet is removed (( M) within 10 seconds while in the OFF state,the device enters the Sleep state. From the Sleep state, the deviceautomatically enters the Automatic Session state when the sessioninterval time has expired (T_(I)). The Automatic Session deliversstimulation for the session time (T_(S)) and the device returns to theSleep state. In this embodiment, the magnet has no effect once theAutomatic Session starts so that the full therapy session is delivered.

While in the Sleep state, if a magnet has not been applied in the last30 seconds (D) and a magnet is applied for a window between 20-25seconds and then removed (M.20:25 s), a Triggered Session is started. Ifthe magnet window is missed (i.e. magnet removed too soon or too late),the 30 second de-bounce period (D) is started. When de-bounce is active,no magnet must be detected for 30 seconds before a Triggered Session canbe initiated.

The session interval timer runs while the device is in Sleep state. Thesession interval timer is initialized when the device is woken up fromShelf Mode and is reset after each session is completely delivered. Thusabort of a triggered session by magnet application will not reset thetimer, the Triggered Session must be completely delivered.

The circuitry that sets the various states shown in FIG. 16 as afunction of externally-generated magnetic control commands, or otherexternally-generated command signals, is the micro-controller U2 (FIG.14), the processor U2 (FIG. 13A), or the control circuit 220 (FIGS. 10,11 and 12). Such processor-type circuits are programmable circuits thatoperate as directed by a program. The program is often referred to as“code”, or a sequence of steps that the processor circuit follows. The“code” can take many forms, and be written in many different languagesand formats, known to those of skill in the art. Representative “code”for the micro-controller U2 (FIG. 14) for controlling the states of theIEAD as shown in FIG. 16 is found in Appendix C, attached hereto, andincorporated by reference herein.

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In the preceding description, various exemplary embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe scope of the invention as set forth in the claims that follow. Forexample, certain features of one embodiment described herein may becombined with or substituted for features of another embodimentdescribed herein. The description and drawings are accordingly to beregarded in an illustrative rather than a restrictive sense and are notintended to be exhaustive or to limit the invention to any precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching. Thus, while the invention(s) herein disclosed hasbeen described by means of specific embodiments and applicationsthereof, numerous modifications and variations could be made thereto bythose skilled in the art without departing from the scope of theinvention(s) set forth in the claims.

What is claimed is:
 1. A method of treating dyslipidemia conditions in apatient using a small, leadless, implantable electroacupuncture (EA)device powered by a small disc primary battery having a specifiednominal output voltage of 3 volts, and having an internal impedance ofat least 5 ohms, the implantable EA device (IEAD) being configured,using electronic circuitry within the IEAD, to generate EA stimulationpulses in accordance with a specified stimulation regimen and apply theEA stimulation pulses through at least two electrodes/arrays located onthe housing of the IEAD to the patient's body tissue at a selectedtarget tissue stimulation site, said at least two electrodes/arrayscomprising at least one central electrode/array of a first polarity,having a maximum width of no more than 7 mm, centrally located on afirst surface of the small IEAD housing, and at least one annularelectrode/array of a second polarity spaced apart from the centralelectrode/array by at least 5 mm measured from the edge of the annularelectrode/array closest to the central electrode/array to the center ofthe central electrode/array, said method comprising: (a) implanting theIEAD below the skin surface of the patient at the selected targetstimulation site, the target stimulation site being selected from thegroup of target stimulation sites comprising acupoint ST40, andunderlying nerves saphenous and peroneal, with the first surface of theIEAD facing inwardly into the patient's body tissue at the selectedtarget stimulation site; (b) enabling the IEAD to provide stimulationpulses in accordance with a stimulation regimen that provides astimulation session at a rate of once every T4 minutes, with eachstimulation session having a duration of T3 minutes, where the ratio ofT3/T4 is no greater than 0.05.
 2. The method of claim 1 furtherincluding setting the time T4 to be at least 1440 minutes [1 day], butno more than about 20,160 minutes [14 days].
 3. The method of claim 2further including setting T3, the duration of the stimulation session,to a value between 20 minutes and 60 minutes.
 4. The method of claim 2further including setting the stimulation pulses during a stimulationsession to have a duration of T1 seconds, that occur at a rate of onceevery T2 seconds, where the ratio of T1/T2 is no greater than 0.01. 5.The method of claim 4 further including setting the time T1 to be 0.1 to1.0 millisecond and the time T2 to be 250 to 1000 milliseconds.
 6. Themethod of claim 1 further including controlling the electronic circuitswithin the IEAD to limit instantaneous current drawn from the small discprimary battery so that the output voltage of the primary battery doesnot drop more than about 11% below the output voltage of the primarybattery when current is being drawn from the primary battery, where theoutput voltage of the primary battery is equal to the specified nominaloutput voltage of the primary battery less the voltage drop caused bythe instantaneous current flowing through the internal impedance of theprimary battery.
 7. The method of claim 6 wherein the electroniccircuitry within the IEAD includes a boost converter circuit, andwherein the method of controlling the electronic circuits within theIEAD to limit the instantaneous current drawn from the battery comprisesmodulating the operation of the boost converter circuit between an ONstate and an OFF state.